Put lightweight curtains over the hardware cloth/chicken wire/screens and keep them damp. That filters out a lot of the ash. You'll need to totally rinse them out frequently, though, as the ash will clog the fires, trapping air and ammonia inside. You can do it while they are still in place, as long as the water doesn't run into the coop. The same trick works for your house windows - damp sheets hung over your screens and cleaned frequently. Both are lessons taken from friends who went through the Camp Fire a while back.
Good Luck ... and stay safe!
