Total Rebuild of a 1979 Dodge Class C

Don't use bondo as it will get hard and crack or just come out. And the resin you have bought at the auto parts store are Polyester resins. This will be a mess as they do not have enough working time, you need epoxy resins for this job. Check Aircraft Spruce and specialty's web site and use any of the epoxy's they sell. Good marine supplys will have west systems epoxy as well. You will be able to get the working time you want and need. Make sure you prime any rustable metal before you apply epoxy or any resin over it. The metal under will rust under it if it's not primed. I build many things out of epoxy resins and fiberglass. Here's a pic of the Observatories we build.



And our web site:

http://astroobservatorys.com/thunderdome/index.html

Just trying to help:)
Terry