Until the 60's most all metal straightening was accomplished with the use of a pick hammer, a body file and a solder box containing the proper elements and tools. The metal used by auto manufactures before the 80's was the cold roll variety with a gauge of 14 to 16 and was very malleable, making it rather soft, easy to shape and straighten with the use of the pick hammer and dolly. A sharp body file was then applied to cut the metal to a smooth finish and to bring out the high and low places.
Where the metal may be a little thin or rough to pick, the body solder (leading) would be applied. This also is where the final finishing will take place with the body file plus more picking to secure a smooth flat surface.
Where soldering is needed the metal must be perfectly clean. All paint must be removed and all rust or other contaminates are removed with the use of a torch for heat and Mauriac acid. (Do not inhale the fumes). An electric drill, air drill or wire brush are also handy to remove contaminants.
The solder must be a 30/70 composition. The 30% tin is needed for tinning the metal and acts as a binding agent so the lead would adhere to the metal surface. Tinning the area where the solder was to be applied was accomplished with the use of a acetylene torch, soldering salts, a stick of solder and a rag.
The area to which the solder is to be added must be perfectly cleaned, solder salts applied then heated hot enough to melt the solder. while keeping the area hot, use a rag to wipe the solder over the entire area to be soldered. Now you are tinned and ready to add more solder to the tinnered area as a filler.
When adding the solder, a wooden paddle is used to spread the solder over the surface. The surface of paddle must be dipped occasionally in heated bees wax to stop the solder from sticking to the paddle.
Soldering is only used when the straightening could not be accomplished with the pick, dolly, and file. Now, what do you think, are you ready to give it a try? You can do it, God did not make any dummies, "Its better to try and fail than to never try at all." I invite you to comments or questions.