It’s a common question, can you paint over polyester primer? Or, does polyester primer need to be primed with a urethane primer?
The answers? Polyester cannot be painted over, but it does not need to be primed. It does, however, need to be sealed. The sealer can be allowed to dry and then be wet sanded, or it can be sealed, and continue ‘wet on wet’ to base coat. Follow the TDS of the sealer for dry times, etc.
The important part if you’re going from polyester, to sealer, to paint. Don’t miss anything! You should be starting to sand your polyester primer with 100 grit. You don’t want to miss any of those scratches, and find them in sealer or base coat. This is why guide coat is so crucial.
More than likely, there will be some sand throughs into the filler. It’s best to use polyester and spot in those areas before sealer. Depending on the situation, that can be done after 220 grit, or after 400 grit, and then final sanded. Just make sure your sealer is going over all primer, and no filler spots.