Are the mites small, white and nearly invisible? Or are they brown, still small and run around like crazy?
Remember, wild birds carry mites. So if you've got birds in your yard, you likely have mites. The point is to contain them to a reasonable level (none is optimal, but realistically, very very very very low is best)
If white - they're immature - be glad! Seven DUST is the way to go. I sprinkle the dust directly on the hens backs, and rub all over their body (avoid the head) - especially the vent/tail area where the mites most likely live.
If brown - they're mature - and you're going to have more. Just re-apply Seven Dust faithfully and eventually they will go away. (for a bad infestation here, I reapplied on the birds every 3 days for a week, then 5 days for another two weeks, then 10 days for another two weeks...and got rid of 'em for the most part).
I found our chick starter feed was infested with the mites. That's how they got into the coop. Because the mites are white/clear to begin with, they are virtually impossible to see. And yes, they did get on me - but once I figured this out - after being out in the coop, I would changed ALL my clothes upon entering the house, and washed my arms in the laundry room sink. Mites cannot live on people, so if they are on you, they will die. I believe it's the same with all mammals...so dogs/cats are immune from chicken mites also. (Now laundry is another issue - I generated three loads a day!)
I finally tracked down that the mites had gotten underneath the linoleum flooring I had in the coop. No matter how much I used Seven Dust, or how much I cleaned, I couldn't get rid of them completely. I changed out the flooring, cleaned/cleared EVERYTHING, used 3 containers of Seven before putting new bedding in the coop - and the infestation finally, finally stopped.
So you might be looking at some drastic measures. I didn't take down the paneling or the insulation - so I might eventually need to. It's been 2 years though and the mites are for the most part gone. I doubt they'll ever truly be 'gone', as we have too many songbirds in our yard. But it's manageable.