Use a Permethrin based spray or dust to treat your hens. Clean out your coop and nesting boxes, treat that too. Repeat in 7-10days.I just found some poultry lice around the vents of my laying hens.... does the Poultry Protector spray from Manna Pro help with this, or should i go with something that seems a big stronger....?
You can find Permethrin at Tractor supply. Concentrate is usually the most economical way to go, get yourself a spray bottle for the hens and sprayer to treat the coop.
Alternatively, its more expensive, but Elector PSP (Spinosad) is a very effective treatment option too.