Ugh, having the same problem here. We have starlings that love to come in and scrounge around for food. They are mite/lice carriers in a major way. So no matter how many times I get rid of the little creepy crawlies they always come back at some point. I use the Sevin spray. It's less messy than the dust. I put a sock over the chicken's head, have someone hold them upside down by the legs and spray them down. It's worked for me every time. I usually only have to do this once a year usually after our first hard freeze. In the spring I clean out the coop and spray it down too. Then I shut the doors so they can't get in for 12 hours. Put in fresh bedding and voila! I've never had a chicken get sick using this method and it saves me from having to deal with the dust. I hate that stuff!
