That's good to know
I don't know anything about bottle caps, just polymer clay. I found out that Sculpey changed their formula for their glossy glaze though, and from what I've heard from my polymer clay friends, its not good. I've heard really good things about Glossy Accents though, including that it works better than DG3 did. I would apply that after all your baking is done though if you are going to use it, and after the mod podge, if you want to add dimension to it. If not, sounds like just the mod podge is a great way to go!!