I do not have experience with Red mites rather Northern Fowl but I used permethrin on both birds and my coop.
I used concentrate and sprayed an empty coop that had been vaccumed. I soaked everywhere with a focus on cracks between the 6" wall boards. Let it dry, added pine chips, let the flock...
You will not be successful in getting rid of mites by sanding and painting.
First confirm what type of mites you have: Northern live on the bird; Red live off the bird and feed only at night. I have read that Red mites are detected by paper towel wiped along the underside of the roost bar.
If...