I think spraying creosote is fraught with risks Darkbrowneggs. It is very thin and penetrates well into the very fine gaps the mite eggs are in. But I find inhaling the fumes in even the smallest amount makes me rather ill. I wish there was something else as powerful against mite. But I've just treated a small coop that had been sprayed twice with Nettex and left with the lid on to 'cook'. It seems all that happened was a few obvious mites were killed but the quick ones made it into the lid under the felt and under the floor to the outside. Obviously they were not previously resident there as there were no nest spots. A lot of eggs were in the tongue and groove as well. When I applied the creosote on the inside, hundreds of newly hatched grey ones rushed to the outside. I had the panels upside down and even put some into the joints from the painted outside, which I wiped off. Still think I may have missed some so that coop is staying out of service for a long time.
Problem is creosote keeps them at bay, but once they have got a hold (last treatment was 15 months ago) it is a hell of a job to kill them all off. Most important is the unhatched eggs which the other chemicals don't seem to touch. You have to wait for them to hatch and treat again -expensive both in time and money.