There's a welder across from where I rent my garage who has interest learning the sheet metal stuff. He helped a little on the Wagoneer and we hope to do more when there's time. Anyway, somehow found this video about showing oxy-acet welding sheet metal panels with minimum distortion.
with Peter Tommasini
I'm sure there's other approaches but he seems to be an old hand that knows his craft.
I did see Greg and Eddie at the shop use a reusable putty of unknown content to keep the spread of heat confined while welding on body panels, at least slow it down some. 3 or 4" on both sides of the weld zone. Vertical or horizontal they built a little levee looking thing. At the appropriate time peel the stuff off throw it back in the can for the next time.
