Here is an article on sealing truck campers and the information applies to travel trailers as the material surfaces are the same.
I'd recommend the same brands and types of sealants, I've used both and they are superior to others. If I have a difference with the article, it is about service intervals (a lot depends on location and UV intensity, along with any snow coverage, intervals would be longer) and the type of caulk remover if silicone has been used. 3M silicone caulk remover followed by a highly aromatic solvent (acetone, lacquer thinner, etc) does a good job for me.
I've also used Eternabond tapes and it is a great product, eliminates a lot of sealant upkeep and will seal problem areas. Any surface that is intended to use Eternabond needs to be scrupulously cleaned before application to get a good bond and the tape needs to be rolled, strongly.
