More on working with lead
You missed something in your answer to the question about using lead (September issue). It’s been 50 years but I recall that you’re supposed to use flux to tin the metal and then apply the lead. Once the lead was filed and sanded you used something—vinegar or ammonia— and water to neutralize any flux that might work its way out and give you bubbles in the paint a year or two later. I’ve seen Bondo and lacquer putty shrink up a year later and crack a year after that. I had a bad crease in a 1939 Plymouth that I filled with lead and from 1970 to 1986 said car had no signs of the repair. Talk to any 80+ year-old body man and see if I’m right. Try applying Bondo 1⁄4inch thick and see what happens. Lead will flex rather than crack and will stop rust bleed-through.
The question you refer to in the September issue asked about applying new sealant and paint over an existing lead repair and my answer addressed that question. What you bring up, neutralizing the flux to guard against subsequent corrosion, is an important step in doing the lead work but has nothing to do with the question asked or the answer given. Neutralization of the flux should be done with a base solution such as baking soda dissolved in water after the tinning butter is applied and heated.