I am in my sixth year with chickens.
No matter what one does chickens will mark walls, dust will magically appear on every horizontal and most vertical surfaces, paint will be pecked & shat upon and there will be more of the same tomorrow and every day there after. Good luck with keeping it clean!
Mites & lice are most often contracted from other animals and birds that chickens encounter. They will be brought into the coop on your chickens and will retreat "into the woodwork" at night or will stay on the bird until the owner intervenes.
In the meantime flock keepers will often encounter the larger pests & predators like mice, rats, raccoons, possums, etc. while wild birds with avian flu will fly over dropping infected "gummy worms".
I have been through two rounds of Northern mites, one of lice, one of worms and a number of predator attacks over my six years. All of this is part of keeping chickens. Neither paint nor caulking will change this.
The best we can do is repeated herein daily.
- Build or acquire a coop you can afford, adjust & secure
- Surround it with a secure, hopefully covered, run.
- Remove waste as often as you are able.
- Watch your birds carefully for infestations, injuries, illnesses and treat (maybe remove) quickly.
- Observe strict bio-security practices
My run is a pole shed with
solid roof and 1/2" hardware cloth on all walls and as aprons extending outside. Took a couple of years before I managed to close every opening. I no longer free range.
My walk in coop
sits on a 4x4 frame that is 3'+ off the ground, access via a stoop 3 steps high. I have never seen signs of mice nor other such critters inside; i absolutely do not have anything living under the coop and the wood it is built from is as sound as the day it was bought.
I believe these last two factors are extremely helpful to maintaining a healthy and productive flock.
Best of luck!