Even if you use the same smooth-on resin they were cast in. It's not going to bond "molecularly." Using smooth on over any sort of fiberglass resin at this point isn't going to be an advantage. Once resin is cured, it's cured.
As long as you give the inside of your gauntlets a thorough sanding for the resin to grip to, and thoroughly clean them out before glassing, you will never have an issue.