Brew stores of course sell grain, they also should sell kits, in the very least extract kits and better stores might even sell all-grain kits. But the best way to learn is to get your own grain, weight it, crush it – this will give you the flexibility you are after, so you can tweak the recipe if you think it would come out better in a slightly different way.
There are basically two types of grain categories base grain and specialty grain.
Base grains make up the base of your beer, that’s why they are called that and typically the American 2-row barley is used for the base grain (but there is also 4 and 6-row too) and wheat too if you are going to brew a wheat beer.
http://en.wikipedia.org/wiki/Barley
As for specialty grain, there are quite a bit of those, a lot actually – so the best way to get familiar with all of them and look at them is to go to your local brew store. Grain is not that expensive, base usually sells for $1.00 per pound, and a typical 5 gallon batch might need anywhere from 8 to 12 pounds of base grain, so you are not talking a lot of money.
Also the better stores will sell 50 lb bags of grain for some additional discount.
To be able to buy grain directly from the Malt house requires a federal license in most cases, which most home brewers lack, unless they also running a micro-brewery in the back of their house or something like that…. :- )
Each specialty grains does something to the beer, to its profile, to its taste, its body, its color, its outcome, and this is well known and so with beer software you can make your very own beers (via trial and error) from scratch if you want!
http://www.beertools.com/html/ingredients.php?view=grains
Take a look at the link above and read what each type of grain does to a beer, takes a while to learn all this, so don’t worry about it.
Most brew stores, the better ones will have a room dedicated to this, if they have the space. Ask the rules if you never been there before, but generally speaking you find your grain bin, weigh the grains in the order that you need them, dump the grain into some bag and as last step you throw all the grain into a mill to crush your grain. The stores mill will be pre-set, as most are.
If you want the grain crushed a certain way other than the pre-set, don’t crush the grain, bring it home with you and use your own technique or mill setup.
There are all kinds of mill setups out there – and so instead of showing one picture, here is a link to the Google search via image and you can see many different setups:
well, that’s it for now – bear needs to go and use the hot-tub.