I too have been dealing with mites in the small coop and on my girls, 9 month old BO and a BR.  I didn't notice anything until I noticed that the tiny creatures were on my hands when I opened the coop door or touched anything - nesting box, hens, etc.  Then we could see them scurrying along the coop frame.  I started with DE about a month ago - really saturated the coop - which has a dirt floor, mixed with pine shavings.  It's very dusty and dry.  The mites were much less noticeable in several days.  I started dusting the hens a couple of weeks ago.  One loves it!  However, I am still finding a few mites again - on an egg, for example, or when I pet a hen.  They free range in the yard almost every day for several hours.
The owner of my feed store suggested using flee powder for kittens.  Most likely this has pyrethrins or permethrin.  I'm going to try that next I think if I can't find poultry dust.  Sorry so many people have the problem but I'm glad I'm not alone in dealing with this.