If you have a feed store, go and ask for poultry dust. They should have what you need to take care of it. Remember to reapply in 2 weeks to get any new hatchlings.
Jody, I got permethrin which is general purpose livestock and poultry dust. I'm planning to dust them this evening... hopefully they'll be relatively calm. I will clean out the coop in the morning after they leave it for free-ranging.
The best time to do it is when they're sleeping on the roost. We just dusted a flock the other night and walked right down the line. Works like a charm. You get a couple cackles and bock bocks, but they don't get crazy as long as you talk to them and their used to your voice.
Yup... all done. I can't walk down the line like you can due to the coop design, but instead had to reach a bit and pulled them over one by one... and honestly it was okay. I ended up finding that Miss Prissy's way of putting the powder in a stocking, worked well. I just dusted them in the bum and under the wings.
I went back to check to make sure they hadn't created a whole lot of dust and they were totally quiet...sleeping. All is good. Now I just have to do it again in 2 weeks.