Polyester VS SPI 2K Primers

[mitch_04]

I have a bunch of panels that have a couple coats of epoxy on them, some up to 2 years old (had a deployment in the middle). I did my best pounding dents out, got them all sanded with 80-220 depending on whether I had some bare metal showing. Now I just sprayed another couple coats of epoxy, then (after a couple days) sprayed a coat of Slick Sand.

I'm now out of Slick Sand and have been reading about polyester primers. It seems that Evercoats 4:1 products or G2 may be my next purchase. However, I'm still slightly confused on it's uses.

Why would you spray a polyester vs a high build 2k SPI primer? And why would you top polyester with a 2K instead of epoxy?

Just a couple things I noticed people doing while researching primers, could use a little help understanding.

 

['68 Coronet R/T]

Think of polyester primer as spray on body filler. It is used when a car has lots of little issues that would require panels to be skim coated with body filler.
You don't shoot paint directly over filler and hence you don't want to shoot your base over polyester primer. The 2k primer will give you a much better surface for your paint when properly prepared.

 

[jcclark]

If your panel is straight after the polyester, you'd be better off
using epoxy over it. It'll seal it better and give better adhesion.
But that's only if they're straight enough to not need the high
fill of a 2K.