you dont need a heating agent really, kief is pretty malleable. there are products called "kief presses" or "pollen presses" (just a euphamism) that you could get, or design something from shit around the house, but im nort really sure how id go about it.
i use a pollen press. after i press it i toss it in the freezer for a day or 2 while its still in the press. comes out perfect. i have a freind with press who is less patient than myself and his method is to press it.....fill a cup with the hottest water u can get from the tap....drop the press in a bag and the bag in the hot water. let the water reach room temp ( about 15 min or so). get ur press and chuck it in the freezer now for 15 min to get it nice and hard. bam ur done. the only problem with this is you can ruin both your press and ur hash if water gets up in there....thats why i only freeze the thing, i aint riskin ruinin my good ass hash just cuz i cant wait a little bit