Body and Paint Questions

OK Rail, first, I doubt they used a waterbase paint, as that technology was not used very much 15 years ago. If you want to do it right, you can continue to sand it down the way you are, when finished spray 2 coats of Epoxie primer, (that is your adhesion coat) then while the epoxie is still active (within 24 hours ) spray 2 coats of polyester primer (Feather Fill, etc.). Then guide coat and block sand dry with 150-180. Once you have it smooth spray 2 coats of urethane primer, guide coat and block with 320 for single stage, 400 for base/clear. You should have a nice straight car when finished.