<Worked with my Dad in our bodyshop in the 50 & 60s this was what we did on autobody work. Back <then we used lead.
Before the days of bondo being invented, solder or lead was applied to the low spots of heated steel auto body parts and spooned smooth. It was a true craftsman who could masterfully apply this stuff. Three and five pound bars of Lead and solder were common items in a auto body shop before the mid 1060's My God, I feel so old just know about this stuff. Please guys, do not use polyester bond on your airplanes. Putting polyester resins on epoxy is a recipe for trouble. They will not bond together properly. Brant Hollensbe West Des Moines Ia. Bhollensbe at mchsi.com