Here is a little info on Brightside. Apparently requires its own thinner, and a max thinning of 10%.
Brightside Spec page

Here is what I am not following. Both Rustoleum and Brightside are "enamels". There is a lot of talk here about final sanding and buffing. I always thought that enamel had a "layer" of gloss, and if you went though that you lost the gloss.

Is that true anymore?