Jiggs, I used to have an older 13' Scamp
with the same walls that you described. I never had to paint
ours, but did read many posts about this very thing right here in the FGRV forum. Make sure you super prep the walls by cleaning with Crud Cutter or something similar. You then fill the seams with a latex calk, using a dampened wadded up paper towel to blot the calk to give it a texture like that of the elephant hide. Once all is dried/cured, use a latex based paint
. Sounds simple, but then again, I've never done it.
Dave & Paula