Be careful using polyester primer as a filler, it will shrink and crack. Use regular filler first....
For general primer with some filling ability, a 2k urethane primer is much easier to work with. Throw in a touch of reducer and it will lay out like paint.
Dont get me wrong the polyester primer is awesome stuff but yeah regular body filler like bondo first on anything substantial. Ive sprayed it on plywood, sanded it and then base/clear black and it looked perfect. Just filled the routed edge with bondo first, slick sand, sand and paint. We use the cheap Smart brand light weight filler or evercoat light weight. For urethane primer we use Axalta - Nason which used to be DuPont. Stay away from the single part glazing/spot puttys too (red stuff in the metal tubes), always use a 2 part. For paint we use BLP Mobile both their mothane line and polyprothane line of acrylic polyurethane. Its good stuff at a reasonable price. Auto paint either Omni (PPG) or Axalta. All the same to me, its the local distributor that makes the difference.Thanks for the heads up on using polyester primer as a filler. So far we have only used it this way for small imperfections.
"Regular filler first?" By this you mean a Bondo-like product?
What do you use, specifically, for urethane primer?
Sounds like your autobody experience is much greater than mine, which borders on none.