You can use seam sealer. Stuff made for tents will work fine.
Be careful about overall sprays: silicon stuff can be bad for vinyl cloth (and really bad for windows).
Our protectant is a UV inhibitor. It works great. I would assume there are others out there that work great too. Anything made for vinyl cloth (think convertibles and boat "canvas") will be OK to use.
VIDEO TIME: (I'm like pimp with these videos!)