Two problems with hydraulic dent raisers. 1. Easy to create a bulge (which is much harder to fix than a dent. And 2. I doubt kdross, or 99,9% of the readers of this board, have one. Hence a pragmatic answer to the need to raise one dent.
And BTW, WW Greener, in his seminal book "The Gun", recommends warming the barrels prior to dent removal. Cold steel is noticeably more brittle than steel at say 300-350F...as some seafarers found out in a famous episode where their icebreaker ship broke to pieces and sunk.
