The old spot putty (NitroStan was the best
) was lacquer primer less some solvent. When I started painting, the first thing you did was to skim the bondo with spot putty to fill the 36# scratches before lacquer primer! Everything was 1K back then except catalyzed acrylic enamel and the occasional Mercedes sprayed with base/clear Glasurit, long before American cars started using it. I remember thinking how awesome that stuff was! I also remember the first base coats from the American manufacturers being lacquer with a "urethane" clear that used the same catalyst as acrylic enamel! The Europeans had about a 20 year headstart on the bc/cc products similar to what we use today.