You see, chemicals exist in different phases: solid, liquid, gas (also plasma but let's not go into that). It is relatively unusual for a solid such as DMT crystal, powder or wax to turn into gas/vapor without passing the liquid stage first. And that is indeed what happens: first it melts, then it evaporates. If you apply a lot of heat, it passes very quickly through liquid into vapor and it might hardly seem like there is a liquid stage at all (apart from the tell that you can lose DMT by it seeping through the mesh in the liquid molten stage). If you apply even more heat, there is pyrolysis: it burns. Instead of simply changing phase, there are actual chemical reactions that change the DMT into other nasty acrid chemicals that are obnoxious to inhale and that are mostly not expected to be psychedelic, not being DMT. If you apply very gentle heat by a) heating from the outside lateral side of the bong cone, b) keeping it at a distance and only very slowly bringing it closer to the prepared DMT hit, then you can melt it with minimal evaporation. (There is not enough energy added - i.e. rise in temperature from the gentle heating - to allow transition into vapor/gas but there is just enough to allow transition into the liquid phase. And yes it is true that it is best to first melt DMT onto the surface of the choreboy metal to ensure maximum benefit (I explained before how/why we benefit). So long story short: yes you basically had it right with the 'applying heat from underneath'.