Depending on what epoxy you use, heating the plug is not always the best thing to do, I was sealing with e-tex, heating the plugs, without issue. But I changed to a penetrating epoxy, and when the epoxy got heated from the plugs, it set the epoxy off, melting the cup it was in and almost causing me some nasty burns. So no heating for me, just pour down through holes, and over surface, perfectly sealed.