Hi, hope you are enjoying BYC!
Sounds like an interesting coop, do show pics!
Only red roost mites care about the wood, and come out to feed at night..
all others live on the birds.. and may come from the environment. I still prefer painted wood for many reasons.
When needed.. (and if you're in the US) a permethrin based horse fly and perimeter spray have been very effective, in my location (both on the birds and in lay boxes, under roost, etc).. Other choices may include Elector PSP or others. I've only needed to treat a total of maybe 4 times, 2 seasons.. out of the 10+ years I've been keeping fowl. So much depends on your location, wildlife load, stock density, weather patterns. even soil type, etc. And I personally don't treat what I don't have under the guise of prevention.. so that way things are still effective when needed.
Diatomaceous Earth.. is not effective AT ALL
in humid environments like mine and also not welcome here. Other dirt bath additions do make a difference when parasites are present.. wood ash is one.
Perhaps, get in the habit (if you're able and would like to) of checking the girls.. once a month is often enough for me and my preferred time frame, but sometimes I only check quarterly every 3-4 months, after dark using a flashlight or headlamp and parting feathers down to the skin.. below the vent and on the abdomen.. look for movement or anything running away. Also take note if the skin is smooth and light pink or yellowish.. or is it angry red with scabby bumps. Are there any dried on looking "dirt clumps" near the base of the feathers that might be nits/egg sacks? Keeping it dim, there's no chasing the birds. Hold their wings down to their back when you take them off roost so their not flapping and freaked out.
Other bugs I have found in the joints of my 100% painted door where it meets the frame/structure and the linoleum flooring (above not below) would actually still include earwigs and pill bugs. That's in my smaller coop, only about 2 feet off the ground.. again very high humidity.. I don't see these in my larger coops. because there's less moist ground and way more structure, I suppose.
Happy adventures!