Resin cures though an exothermic reaction... It cures by the heat that is generated when the two chemical react... meaning that stuff that doesn't cure can be heated up to fix it.
But heating up just one spot will probably warp your helmet... or catch fire. So I wouldn't get a heat gun anywhere near it..
Let it sit in the sun for a few hours, and it should be fine.
yeah i was stumped on that to, i left it outside for a day and it was dry so i brought it in. the next morning it was wet in a bunch of places. so i let it dry for the next day and the spots were still wet so i put it in front of a fan and that didnt do any thing so i blew it with a blow dryer and it dryed up. i came back in about an hour and it was wet again.
i had no idea what to do with it so i put another coat on and its fine now