I tried the other day to rescue my frosted minis with a coat of Glosscote.
Here is what I got:
One side of the minis is quite good. The other, still frosted and grainy. I think I got a more consistent coat on one side. So clearly it's working, but I need another coat, and a more consistent coat on the opposite side of those minis.
Next time the humidity drops below 50% and the heat to 70 or less, I'll try again to re-seal them.