Please? 3m says that major pitting is exactly one of the uses for their product, Bondo. It is perfect for it. And 2 part
high-build primer (every can i've used)clearly says it's main purpose is for filling fine scratches, generally as a finish coat to bondo--a modern replacement for the old red lacquer putty. The problem with spraying it as a filler for pits is that you are fighting telegraphing--the area around the pits builds up too so your just looking at a thicker version of what you had. There are sprayable fillers( just thinned down bondo)--not so good I think. I don't think anyone suggested putty without hardener. Bondo(plastic filler) is fiberglass resin(polyester) thickend with Talc, or fumed silica, and hardened by methyl ethyl keytone peroxide. I think leading is fun and easy and ,as stated above , a bit of a lost art--it's nice to know that your repairs are not plastic. There are several threads here where people made nice dent repairs with brazing and Taco Chris has one showing very nice, patient repairs with his welder and a file. Maybe your thing is the quickest and easiest(most certainly regular bondo if the pitting is profound) but the other advice incorrect? Please