This is coming from a 20 year in the business guy. I tried that whole torch thing to fix the oil canning. Yea. It didn't go so well. It was a extreme spot thou. Dead center of my 69 roadrunner hood. Someone had beat the tar out of it with a ball peen hammer decades ago. It was filled with bondo and painted. Well as you get to know me y'all will realize I can't leave crap alone. Decided to grind the bondo out and tried to dolly most of it out. It started oil canning bad bad. Tried the torch method by heating a spot till the metal started moving and cooling with water. Now the hood is so hard it has become brittle and I'm scare it will crack. Long story short. Try the shrinking disc. If that don't work. Find a professional. And that's coming from a "professional".