I use Kyrlon sprays, in gloss and matte and never had a problem with yellowing. I have models that I used it on that are ten years old and look fine. I usually start with the gloss and use a few coats of that first , then decals and weatherizing with a couple of coats of matte to end with. It's definitely good to put at least one coat of gloss over decals or two to blend the excess in, then use the matte. Go easy though, spray very lite coats on at a time to begin with, especially on the decals.
Trekmodeler uses them too and his builds are fantastic.