Larry,
As you're "sealing" and covering the trailer with glue and canvas, the wood will have the potential to be 100% encapsulated...on the outside.
Areas of concern will be cutouts, penetrations, and areas out of sight, such as wheel wells and the bottom of the walls that face the road.
You are probably on top of all this already, but these areas are often overlooked, with the result being ruination of a project someone gave their all to, but simply didn't understand how one pinhole can allow moisture to get behind the best sealed wall or roof in the world.
Attention to the most minor details is the key to success.
Rob
Waiting for "someday" will leave you on your deathbed wondering why you didn't just rearrange your priorities and enjoy the time you had, instead of waiting for a "better" time to come along...