When my chickens have mites I don't see them on them. However I get itchy and find them floating up dead in the bath water. So I can ID the bug. They also bite me. (They cannot breed on human blood but do bite humans.)
You are supposed to look for dark colored bugs (mites) under the wings and near the vent area of the chicken. Lice are straw colored I have read- haven't dealt with those.
I treat with Permethrin dust (the coop and the birds) repeating at 7 days (for lice you need to treat at 14 days). I tie off an old sock and put the dust in it to dust them. Get under the wings and the vent area- everywhere but the face.
Make sure you toss all shavings including nestboxes during treatments or they will be back!