I can't tell you that I have any serious experience, but here's one suggestion:
I let "some" -- I really mean like 5 or 6 plants, just for fun -- Hulless Oats grow until they formed grain. I haven't tried any other kind of oats so there's no real basis for comparison, but these basically slip right out of the chaff. For my trial threshing of rice, on the other hand, I had to beat them up in a jelly bag with a rolling pin
I got the Hulless Oats as cover crops and for kitty greens from Johnny's Selected seeds.