I had my 1940 Ford metal cleaned with blasted walnut shell media. This media is gentle, but, will remove Bondo, easily. The walnut media removed the OEM tar like under-coating and some ridiculous paper material mixed with tar, most likely intended for sound insulation.
Sheetmetal is not able to deal with the sudden rise of surface temperature from being blasted with sand or glass beads. This causes the metal to distort and buckle. The aggressive nature of sand will open the surface of the sheetmetal and the metal will start to oxidize almost instantly. Glass bead blast is less aggressive.
My, now deceased, friend had his 1948 Ford sand blasted. A decade later the paint is bubbling from the oxidation, aka rust, that is growing under the paint. This '48 Ford is not repairable for any reasonable cost. Redi Strip may be the only option for this car or scraping it.
https://www.redistripco.com/contact/ Rust never rests. If you cover rusted parts with replacement panels, the rust will continue to grow out of sight until it arrives at the surface. There is not short-cut to the best outcome.