If yo ukeep the coop clean, red mite shouldn't be a problem.
Most of us Red Mite Powder (which you normally get from garden centres or farm shops that sell chicken stuff) - that's actually its title, so don't worry about getting it mized up with anything else!
then you spread it around the coop once you've cleaned it (at dusk, so that it has an immediate effect), especially in any nooks and crannies
on that first day, also put it on your hens when they go to bed.
