I’m restoring some bee boxes at the moment. Some were really bad, some not so bad. After sanding back to bare wood & replacing the rotted parts with donated wood from hoop pine furniture, I’m soaking them in copper naphthenate. Then after that is completely dry, I’ll bog up any gaps before giving them 3 coats of paint inside & out.
I’d say that this next photo shows the most extreme restoration, the box contains 58 screws in total.