Today I worked on getting rid of three medium size oil canning spots on the roof of my car. No oxy/acetylene torch so I used what I had which was a propane bottle. Things didn't go easy but I ended up getting it done.

When hammering on the spot do you to prefer to hammer before or after quenching? The guy in this video does it both ways.

https://www.youtube.com/watch?v=GN4RosIrEPg

And also I've been considering getting a shrinking disc and I'm wondering if it's good for fixing oil canning?