Well, my
experience is that during the day, they (the mites) tend to retreat and hide at each end of the perches, they crawl back out as soon as the chickens have gone in - for a feast. That's when they turn from grey to red, after they've gorged on blood. I smother each end of the perches with a thick blob of vasseline, it makes it very difficult for them to crawl out of that. I also wipe the perches with a cloth saturated with neem oil.
Egg boxes have a similar sort of treatment. I dilute 1 tablespoon of neem oil with a teaspoon of washing up liquid, add 1 litre of
water and spray all the boxes at cleaning time. Of
course, the bedding gets a good dose of DE.
It has worked remarkably well for me. I do get a one litre of organic neem oil on Amazon France for less than $20 and it goes such a long way.