Chicken mites are little spiders with 8 legs and oval bodies, while chicken lice are even smaller and insects to boot with 6 legs and segmented bodies. The same insecticides that will kill one will kill the other but it may not CONTROL the target species, that is why you need to know which pest you are dealing with.
To kill (control) mites living part time on the pen or coop, mix one pint used motor oil with one pint diesel fuel and add 2 ml of liquid GuardStar 40 insecticide, mix well and then use an old paint brush to coat the roost, dob the cracks, and wooden coop joints. That way if the birds are also treated with a water based premise spray or dip the mites are denied a safe heaven or sanctuary from which to recolonize the flock.
A equal amount of GuardStar 40 mixed with a liter or quart of water makes an effective premise spray, and a little puff of this spray on the rump, on the back, and under each wing will kill both mites and lice. It can also be applied at night with little difficulty. Like Michael I dislike dusting because it needs to be repeated before control is established, however a little Sevin 5% Dust in a location where chickens dust themselves without my having to do it is a gift to Miss Chicken Mite that just keeps on giving.
A dip works well on livestock like chickens but it can be a little messy,
and even though I have dipped my share of chickens I did not think there was anyone left as old school as that. Good luck Michael.