No <expletive> about not using a heat gun on high. I'd be afraid to even use it on low.
Ultimately ended up having it done by somebody who actually has a clue what he's doing.
After getting a quote from my mechanic for $200 (if he could do it paintless) to $400 (if paintless didn't work), I looked around for a specialist, and found one, only a few miles away, who quoted me $85 for paintless, 70% or better. He used a fixed infrared lamp to heat the area, and the result (after no more than half an hour of sitting around his waiting room) was so good, I couldn't even tell that it had been dented.
James H. H. Lampert