the best i have seen
was a guy heated up the dent red hot then turned of the oxygen
and poked the acetelene in the end ,went fuggin bang and jumped about 6 feet off the ground
loud as shit like an acetelene bomb every workshop within 500 meters came out to see what happened
my ears rang for about 30 min :'( actually got 90 % of dent out
not recommended though only trained proffesionals or tools should attempt this procedure
it ran last time i started it