Freezer method is probably the safest.
I recommend if you are going to torch it and pressurize it, fill the pipe with water 95%, then apply compressed air. The less compressed gasses in the pipe, the safer it will be.
Water does not compress, so it has no energy if the pipe were to burst.
Filled only with gas, the release of pressure would be violent. -BIG DAN
Where's the fun in that?The easiest solution is to hand it to someone else and pay the man!
I bought a supposed barely used Oem 89 CR250 FRONT PIPE with one dent from eBay USA somewhere called wapwallopen??? for my restoration and had to have 13 dents removed
Steel pins wer. Welded onto the centre of each dent and under heat pulled out and the remaining Weld ground and sanded off, prep then paint then took the bike to a show and won an award so a little pay in the right pocket pays its way time and time again!
I dunno! I couldn't find itWhere's the fun in that?