The lice problem started with Lou my banty cross rooster (who I am looking to rehome by the way). I have scrubbed the coop from top to bottom and the roosting stick and nesting boxes with soapy lysol water and haven't seen any bugs since. I am so mad at the guy who gave Lou to me it's not even funnyYou can use Killz but it won't help with the bugs. If it was my coop, I'd dust all of the birds for lice and then remove them from the coop and put them in a temporary pen for a few days. Remove all of the litter and clean every square inch. Spray all of the perches and crevices with bird mite/lice spray. Put in new shavings dusted with a good amount of DE in it. Make sure the DE gets into the crevices/corners. Let the coop sit empty for a couple days. Dust your chickens before you add them back to the coop. You might have to repeat this process in two weeks. Oh, and DE their run as well. The lice come from wild birds so make sure you don't have any wild bird feeders near your coop.

What else do they need ready access to besides food, water, dust area and grit?