I guess anything will do that generates/provides organism since that's the worms' diet. You are not after the castings/compost so it doesn't matter. Just keep an eye at the moisture level and don't add too much wormchow at one time. Just do a light dusting or sprinkling until you know how much they can take.

Correct me if I’m wrong but from my research flour is bad but wheat flour is good. I think it was self rising four is bad. I use oatmeal, corn meal, eggshells and sugar. I put in in a my bullet and turn it into powder. They do come to the top to eat it. Check out the flour thing.