I know how to make gluten from wheat flour. I've made my own by adding water to wheat flour until it was a stretchy dough. I washed it until the water ran clear. What I was left with after the starch was washed away was a glob of very stretchy protein Is there a way to use this to make my own powdered gluten?
I would imagine you could cut your gluten dough into small pieces, dehydrate them, and then grind them. You would just have to be sure that you were getting it completely dry and grinding it very finely. This should work, though I don't know how practical it would be.