Most grains in bulk are shipped in closed hoppers with Pnuematic Unloading. Door bottom types were used before Pnuematic Unloading came into use. The type processing would determine the type cars used for shipping. Milled grains(flours) would probably be shipped in "Airslide" type hoppers. Smaller quantities are shipped in bags, barrels or sacks in boxcars.
Grains are used as foodstuff for humans and animals. More information is included under each type.
Some of the types of grains and their varieties are listed below.

AMARANTH: Amaranth is not a true cereal grain at all, but is a relative of the pigweeds and the ornamental flowers we call "cockscomb". It's grown not only for its seed, but for its leaves that can be cooked and eaten as greens. The seed is high in protein, particularly the amino acid lysine which is limited in the true cereal grains. It can be milled as-is, or toasted to provide more flavor. The flour lacks gluten, so it's not suited for raised breads, but can be made into any of a number of flat breads. Some varieties can be popped much like popcorn, or can be boiled and eaten as a cereal, used in soups, granolas, and the like. Toasted or untoasted, it blends well with other grain flours. NOTE: Like some other edible seeds, raw amaranth contains biological factors that can inhibit proper absorption of some nutrients. For this reason amaranth seeds or flour should always be cooked before consumption, whether for human food or animal feed.

BARLEY: Barley is thought by some to be the first grain ever grown by man. It has short, stubby kernels with a hull that is difficult to remove. Excluding barley intended for malting or animal feed, this grain is generally consumed by humans in two forms. Most common is the white, highly processed pearl barley with much of its bran and germ milled off along with its hull. It is the least nutritious form of barley. The second offering is called pot or hulled barley and it has been subjected to the same milling process as pearled, but with fewer trips through the polisher. Although it can be milled into flour, barley's low gluten content will not make a good loaf of raised bread. It can be combined with other flours that do have sufficient gluten to make leavened bread or used in flat breads. Barley flour and flakes have a light nutty flavor that is enhanced by toasting. Whole barley is commonly used to add thickness to soups and stews.

BUCKWHEAT: Buckwheat is another of those seeds commonly considered to be a grain, but which is not a true cereal. It is, in fact, a close relative to the docks and sorrels. The "grain" itself is a dark, three cornered seed resembling a tiny beechnut. It has a hard, fibrous hull requiring a special buckwheat huller to remove it. Here in the U.S., it is most often used in pancakes, biscuits and muffins. In Eastern Europe and Russia it is known in its toasted form as kasha. In the Far East, it's often made into soba or noodles. It's also a good bee plant, producing a dark, strongly flavored honey. The flour is light or dark depending on how much of the hull has been removed before grinding. Dark flour is much more strongly flavored than lighter flour, but because of the high fiber and tannin content of its hull it is not necessarily more nutritious. Buckwheat is one of those foods with no middle ground in peoples opinions -- they either love it or they hate it. Like amaranth, it's high in lysine, an amino acid commonly lacking in the true cereal grains.

CORN (maize): Corn is the most common grain crop in the U.S., but it is mostly consumed indirectly as animal feed or even industrial feedstock rather than directly as food. As one of the Three Sisters (corn, squash and beans) it was the staple grain of nearly all of the indigenous peoples of the American continents before the advent of European colonization. It comes in an amazing variety of forms with some being better suited for a particular purpose than others. The varieties intended to be eaten as sweet corn (fresh green corn) are very high in sugar content and do not dry or store well. The other varieties are the flint, dent, flour, and popcorns. All of them keep well when they have been properly dried. To a certain extent, they're all interchangeable for purposes of grinding into meal (sometimes known as polenta meal) or flour (very finely ground corn, not cornstarch), but some make better meal than flour and vice versa.
As a general rule of thumb, the flint varieties make better meal as they have a grittier texture than the other corns. If meal, hominy and hominy grits (commonly called just "grits") are what you are most interested in, use the flint type. If you intend to make corn masa for tortillas and tamales, then the flour type is what you want, but it is seldom found on the commercial market so the dent type is next best. Popcorn is what you need if you want to pop it for snacks and it can also be ground into meal or flour. It seems to me it makes a very good meal, but it's a bit gritty for flour. It's also difficult to hull popcorn with alkali treatment though your mileage may vary. Yellow dent corn seems to be the most commonly available variety among storage food dealers and will work fine for almost any purpose but popping.
Popcorn is one form of a whole grain available to nearly everyone in the U.S. if they know where to look. It is so popular as a snack food, particularly in movie theaters and events like fairs and ball games, that even the smallest of towns will generally have at least one business selling it in twenty-five or fifty pound bags. Since it's meant to be eaten it's safe for food. To be at its most "poppable", this corn needs to have a moisture content between 13.5%-15.5% which makes it just a little too moist for ideal storage. A small amount of drying will need to be done before it's packed away. If wanted for popping later, it can always be re-hydrated by sprinkling a tablespoon of water per quart of kernels, shaking vigorously and allowing it to be absorbed for a day or two. If you still get too many "old maids" or unpopped kernels then repeat the process once more.

MILLET: Millet is an important staple grain in North China and India, but is little known in the U.S, where we mostly use it as bird feed. The grain kernels are very small, round, and usually ivory colored or yellow, though some varieties are darker. A lack of gluten and a rather bland flavor may account for the anonymity of this cereal. Millet has a more alkaline pH (and a higher iron content) than other grains which makes it very easy to digest. A major advantage of millet is that it swells a great deal when cooked and supplies more servings per pound than any other grain. When cooked like rice millet makes an excellent breakfast cereal. It has little gluten of its own, but mixes well with other flours.

OATS: Though the Scots and the Irish have made an entire cuisine from oats, it is still mostly thought of in the U.S. as a bland breakfast food. Seldom found as a whole grain, it's usually sold processed in one form or another. Much like barley, the oat is a difficult grain to separate from its hull. Besides its longtime role as a breakfast food, oats make an excellent thickener of soups and stews and a filler in meat loafs and casseroles. Probably the second most common use for oats in America is in cookies and granolas. A little creative thought can really increase their culinary range. >BR> Listed below are the forms of oats found in this country. Rolled and cut oats retain both their bran and their germ.
Oat groats: These are whole oats with the hulls removed. They are not often found in this form, but can sometimes be had from natural food stores and some storage food dealers.
Steel cut oats: Also known as Irish, pinhead or porridge (but so are rolled) oats. These are oat groats which have been cut into chunks with steel blades. They're not rolled and look like coarse bits of grain. This form can be found in both natural food stores (sometimes much cheaper) and many supermarkets.
Rolled oats: These are also commonly called old fashioned, thick cut or porridge oats. To produce them, oat groats are steamed and then rolled to flatten. They can generally be found wherever oats are sold. They take slightly longer to cook than do the quick cooking oats, but they retain more flavor, texture and nutrition. This is what most people will call to mind when they think of oatmeal.
Quick cooking rolled oats: These are just steamed oat groats rolled thinner than the old fashioned kind above so that they will cook faster.
Instant rolled oats: These are the "just add hot water" or microwave type of oat cereals.
Whole oats: This is with the hulls still on. They are sold in feed & seed stores and sometimes straight from the farmer who grew them. If you buy from a seed supplier, make certain that they have not been treated with any chemicals that are toxic to humans.

QUINOA: Quinoa is yet another of the grains that is not a true cereal. It's botanical name is Chenopodium quinoa (pronounced "keen-wah"), and is a relative of the common weed Lambsquarter. The individual kernels are about 1.5-2 mm in size and are shaped rather like small flattened spheres. When quinoa is cooked, the germ of the grain coils into a small "tail" that lends a pleasant crunch. This exotic grain should be thoroughly washed before cooking in order to prevent it from tasting bitter and most retail offerings already have been. There are several varieties of quinoa that have color ranging from near white to a dark brown. The larger white varieties are considered superior and are the most common.

RICE: Rice is the most commonly consumed food grain in the world. The U.S. is the leading exporter of it, though we actually only produce about 1% of the global supply. The majority of the world's rice is eaten within five miles of where it was grown.
Rice comes in a number of varieties, each with different characteristics. They are typically divided into classes by the length of their kernel grains; short, medium and long.
Short grain rice: The short grain variety is a little softer and bit moister when it cooks and tends to stick together more than the longer rices. It has a sweeter, somewhat stronger flavor than long grain rice.
Medium grain rice: The medium grain variety is not very common in the States. It has flavor like the short variety, but with a texture more like long.
Long grain rice: The long grain variety cooks up into a drier, flakier dish than the shorter types and the flavor tends to be blander. It is the most commonly found size of rice on American grocery shelves.
Each of the above may be processed into brown, white, parboiled or converted and instant rice. Below is a short discussion of the differences between the various types.
Brown rice: This is whole grain rice with only the hull removed. It retains all of the nutrition and has a pleasant nutty flavor.
Converted rice: Converted rice starts as whole rice still in the hull which undergoes a process of soaking and steaming until it is partially cooked. It is then dried, hulled and polished to remove the bran and germ. The steaming process drives some of the vitamins and minerals from the outer layers into the white inner layers. This makes it more nutritious than polished white rice, but also makes it more expensive.
White rice: This is raw rice that has had its outer layers milled off, taking with it about 10% of its protein, 85% of its fat and 70% of its mineral content. Because so much of the nutrition is lost, white rice sold in the U.S. has to be "enriched" with vitamins to partially replace what was removed.
Instant rice: The type of rice is fully cooked and then dehydrated needing nothing more than the addition of water to reconstitute it. In a pinch, it's not even necessary to use hot water. The white variety is by far the most common, but in the last few years instant brown rice has made an appearance on the market.

RYE: Rye is well known as a bread grain in the U.S. It has dark brown kernels longer and thinner than wheat, but less gluten. Bread made from this grain tends to be somewhat dense unless gluten is added (often in the form of a lot of wheat flour) with color that ranges from pale to dark brown. German pumpernickel, made with unrefined rye flour and molasses, is the darkest, densest form.

SORGHUM: Sorghum is probably more widely known here in the States for the syrup made from one of its varieties. Also known as "milo", it is one of the principle cereal grains grown of Africa. Its seeds are somewhat round, a little smaller than peppercorns, of an overall brown color with a bit of red and yellow mixed in. The varieties called "yellow endosperm sorghum" are considered to have a better taste. It is a major feed grain in the Southwestern U.S. and is where the vast majority of the national production goes. Like most of the other grains, sorghum is low in gluten, but the seeds can be milled into flour and mixed with higher gluten flours or made into flat breads, pancakes or cookies. In the Far East, it is cooked and eaten like rice, while in Africa it is ground into meal for porridge. It's also fermented for alcoholic beverages.

TEFF: Easily the smallest of the grains, teff kernels are only about 1/32nd inch in diameter. The name itself means "lost" because if dropped on the ground, it's too small to recover. It's been very little known until recently, but has been a staple grain in Ethiopia for nearly five millennia. Small amounts are now being grown in South Africa and the United States. This grain ranges in color from reddish brown to near white. It has a protein content in the 10-12% range, good calcium and a useful source of iron. It is traditionally used in making the Ethiopian flat bread "injera", but has no gluten content of its own. It'll combine well with wheat flour though and has something of a sweet taste.

TRITICALE: Triticale is not a creation sprung from the smooth brows of Star Trek script writers. It is, in fact, a cross or hybrid between wheat and rye. This youngest of grains combines the productivity of wheat with the ruggedness of rye and has a high nutrition value. The kernels are gray-brown, oval shaped larger-than-wheat and plumper than rye. It can be used in much the same way as either of its two parents. It will make a raised bread like wheat does, but the gluten is a bit weak so wheat flour is frequently added to strengthen it. Because of the delicate nature of its gluten, excessive kneading must be avoided. Although it is the youngest of the grains, it's been around for decades, but has curiously never achieved much popularity.

WHEAT: Wheat comes in a number of different varieties. Each variety is more suitable for some purposes based on its characteristics. The most common classifications for its varieties are spring or winter, hard or soft, red or white.
The hard wheats have kernels that tend to be small, very hard and with high gluten contents. Low gluten wheat does not produce as fine a loaf as high gluten wheat, though it can still be used for yeast breads if necessary. As a general rule, hard varieties have more protein than soft varieties.
The soft wheats have kernels tending to be larger, plumper and softer in texture than hard wheats. Their gluten content is less and are used in biscuits, pastries, quick breads, pastas, and breakfast cereals where a higher gluten content would contribute an undesirable tougher texture.
Winter wheats are planted in the fall, over winter in the field and are harvested the next summer. Spring wheats are planted in the early spring and are harvested in the fall. Red wheats comprise most of the hard varieties while white wheats comprise most of the soft. Recently, hard white wheats have been developed that are very suitable for raised bread making. Some feel the hard white varieties make a better tasting whole wheat bread than the hard red.
The hard red varieties, either spring or winter, are the most commonly stored because of their high protein and should have no less than 12%. The hard white spring wheats are still relatively new and are not yet as widespread. They have the same excellent storage characteristics as the hard red wheats.

GRAINS AND GLUTEN: Gluten is the protein in grains that enables the dough made from them to trap the gasses produced by yeast fermentation or chemical reaction of baking powder or soda and in turn causes it to rise. The amount of this protein found in different grains can vary radically. Some grains such as rice have virtually no gluten at all and will not produce a raised loaf by itself while others like hard winter wheat have a great deal and makes excellent raised bread.