I had trouble with mites a while back. I did not use shampoo on flock since it was a nightmare on the few I did use it on, although the blow dryer seemed to help kill them (a family I know, only member didn't get lice was the one who used dryer, is why I think this). I got a cheap, lidded, clear plastic tub from the Dollar General that was just a little bit shorter than my smallest chicken. I put a mix of diatomaceous earth, Sevin dust, and the livestock dust for mites in it. I'd say 1/2 DE, and a 1/4 each of the others. I made the chicken squat in the tub so I could get their butt in the dust, then held them with their head out of the tub so they wouldn't breathe it as I scooped the dust onto them as I lifted, seperated, and fluffed their feathers. The ones who had head/neck lice were the hardest - I had to be really careful. When I was sure I had gotten the dust all the way down to their skin, I held them over the tub and gently fluffed them again to get out as much excess as possible, and did it again in the yard before closing them up for the night. Do not get too much dust in their coop, it will cause breathing problems - I did that! Clear everything out, if you can get some Oxine, spray the inside down with it diluted. If you can't get in the coop, use a sponge mop. One type of mite crawls on the bottom of the roost at night. Mites treatments have to be repeated: they lay eggs, so you have to come back and treat again to kill the new ones.