I need to primer my '73 Nova. Im looking for some black primer but for quite some time i've been told that i cant use primer sealer if i want to paint the car later. is that true at all? i've been using sandable primer. i have to keep wetsanding it every month or so to get the surface rust off. i want the car painted, but at a much later time when i can afford it. i'd like a primer sealer to keep the car from rusting in the meantime and still be able to leave it out in the rain if need be with no worries. any help is appreciated.