put specialty grains into a plastic ziploc bag. put just enough so that it lays flat with only 1-2 layers of grain. put bag on top of dish towel, put another dish towel on top. using rolling pin or wine bottle to crush grain. empty and fill ziploc and repeat. you want a gentle crush, not flour.
I crush mine with a rolling pin and ziploc bag--towel under but not on top. The key seems to be not overfilling the bag. You want to use medium pressure, inspecting the grains after each pass or two. The goal is to split and open the husks without pulverizing the husks.
No, I don't know what the heck I'm doing. But it seems to work. Having your grains crushed with a dedicated mill is still best.