I am a fan of Sevin dust, too. But since the govenment stopped letting us by it in bulk here, it's impossible to use in a large covered walk-in chicken yard like mine. I changed the straw in all the nest this week and put sevin in the bottom. But I believe I also have the yard mites under control. I got about 100 pounds of DE and poured it out all over the chicken hard and the coops, too. Afterwards it looks like Anarctica but I think I've killed most of the mites. Ivermectin went on their behinds and afterwards NuStock on any inflamed areas. After the next rain, I'll do the DE again.
I still don't have any wood ash.