I haven't painted or varnished or stained my DIYS timber vivs (my BTS live in).
I simply wipe down with clean damp rag , follow up with dry paper toweling and then spray the cleaned surfaces with F10SC made up 1:125 in water , let stand and air dry.
I have loose laid tile over aluminum foil under my BTS bedding (a mix of course dry Kritters' Krumble and dry gum tree leaf litter and twigs. The aluminum foil under tiles stops any moisture from reaching the timber.
I have similar less the bedding for my dragons. I simply remove the soiled tiles , take them outside, place on the grass and blast the heck out them with a garden hose to clean them.