One of my roos had scaly mites really badly. We used an old-timey cure that cleared him of the mites in a month. We got him from a neighbor and he had scaly mites so badly one of his toes fell off. His feet were also permanently disfigured for the rest of his life. That being said, this cure works like a miracle and he got such relief from it he would coo while we soaked his feet.
Do this every night until their condition improves:
1) Soak their feet and legs in warm soapy water to soften the scales and drown the mites. Gently dry their legs, don't scrub or anything.
2) Make a dip of the following in a non plastic container
- 2 parts linseed oil
- 1 part kerosene
3) Dip their legs in the linseed/kerosene. Don't get it in their feathers. Dab dry with an old shop towel.
Also, during the day paint their nest boxes and perches with the kerosene/linseed oil. You will also have an infestation in the coop which will spread to other hens. Make sure you do this in a well ventilated environment, too.