IamSamSam
Songster
Tee tree oil, mixed with a little eucalyptus oil.
Lice and mite both hate it.
A good option is tea tree cat shampoo add about 5 drops of eucalyptus . If you give your chooks a warm bath in the stuff for about 10-20 mins(Don't let them drink it) and dry them with a hair dryer it will kill almost any external bugs they have.
Sounds good. But I don't like bathing chickens. It's not fun.