My wife laughed when she first saw my milling operation. We buy certified organic whole grains and grind as necessary. I toss them into the hopper to be ground to the size i want (I have a couple of different size screens - peeps get a finer grind then the big girls), ground grains drop into the cement mixer for a few spins before I dump into the 5 gallon bucket. You have to take note that all grains once ground begin to break down - I don't want my girls to eat rancid food.
Polyunsaturated fats easily turn rancid simply by exposure to heat, light, or air, making them very unstable.