There is some info on priming here
They seem to rely on alclad and wash primer for sheet and the preassembled main spars are gold anodised. They clearly state that rod/angle should be primed or anodised before installation.
Re wet assembly - I've done a little further reseach on common industry practices (I'm sure they vary from company to company). It seems the protection measures are dependant on the joint materials in contact, the fastener material and fit (ie close tolerance or clearance) and the environment. So for example, a clearance fit bolt joining dissimilar materials is more likely to be wet installed than rivetted ali sheet of the same material. Anything in a maritime environment is likely to get full wet assembly everywhere. Measures are generally some combination of faying surface seal, edge fillet, shank and/or head and tail wet install. The large areas of ali riveted 2024-T3 sheet (all same material) on the RVs may not warrant any special treatment if you keep it out of the weather and don't live by the coast.
All complete speculation and opinion of course.