One of our chickens has mites. We can tell because a few of her scales on her legs are lifting which we found out is a sure sign of mites and if one chicken has them they all have them.
We spoke to the person we purchased our chickens from as well as another farmer and both said the same thing...WD-40.
Art caught the chickens, no easy task, and sprayed their legs while holding them upside down so the spray has a chance to roll under the scales. They are squawking and running and none too happy. But they are all sprayed, their coop is clean and agricultural lime and DE is sprinkled on their perch, nesting boxes and the floor.
I'm sure they will be happy chickens in the very near future.