Sealing wood on a trailer?
Well there is one other option that would most certainly seal the wood and that would be to use Kool Seal on the entire trailer. I used it on the roof and am thinking of using it on the walls. It now comes in a white color. Although it may be sprayed, even though its kinda of think I believe I would prefer just brushing/rolling in on.
For those of you that know nothing about Kool Seal, its the stuff that is used for sealing the roofs of mobile home trailers, but wait! one more thing comes to mind. If you are not picticular of how the trailer looks on the outside you could also have bed liner spray, sprayed on the trailer, then coming back with white paint.