It's permethrin dust, fine, but won't do the vertical coop surfaces, and costs more than the spray concentrate. Best in very cold weather on the birds though.
Best to always wear a N95 dust mask, or respirator, when cleaning the coop or using any products out there!
Mary
And it's best to NOT use carbaryl, it's not approved for chickens in the USA. That's why permethrin is the product of choice, approved, and no egg withdrawal.
Mary
I think this week will be glorious! Also fine to spray the coop and birds, at night, later in the week when it's positively balmy for November. We'll be spraying it here too.
I've never had to treat for scaly leg mites, fortunately.
Mary