After having a mites infestation last fall I now do preventive, I use Epernix pour-on there is no egg withdrawl and you can get it at Tractor Supply or order on line.. 4 drops for small fowl, 6 drops for large fowl put at base of neck on the skin between the wings.. this will also kill internal parasites. I also treat the coops with DE,Poultry protector and even sevin if needed.
I use the eprinex also twice a year (spring and late fall), and may alternate valbazen in. I usually put sevin dust along edges of coop inside and use pine shavings which get scooped daily and usually need to add some by week's end. Sometimes I spray permethrin on roosts and near walls where ants, etc. might try to sneak in.