In my experience the GVG is almost too smooth when you get that heating down.
Its a damn shame that i hid mine in a box in a paranoid moment and forgot about it, only to drop something else into the same box a week later and crush the damn thing.
Talk about butt hurt.....
But yeah, if you are getting a strong burnt dmt taste or any harshness i'd say you either have contaminants in your spice or you are applying too much heat. I'd also recommend against the heating first, pulling second method. I might put the flame to the pipe for a brief second before i inhale but I can't imagine it would be pleasant to do what you tried. No offense is meant by that, i just mean i can imagine that the hit would have been far too much. I struggled at first as well so i can relate.
I find that good clean DMT, properly vaporized, has little to no taste at all. If anything it would be a very light and more floral taste. Very smooth. The moment that spice burns though.... YUCK TOWN!!!! And good luck holding in a big harsh dmt rip. I tried with a meth type pipe ONE time before realizing that there was no way in hell i was going to get the heat application correct on that style.
I would also like to add that making a little machine type pipe would be a wise idea until you have time to practice with the GVG. I hate to see anyone wasting spice!
The great thing about the machine is that it is almost IMPOSSIBLE to screw it up.
Good luck! Safe travels!