Can't comment on SPI, have not used it , yet. In my beginning days I was advised to use PPG brand epoxy primers and since have tried two of the cheaper brands Mastercraft and Transtar, and PPG wins over them hands down. But will seek to get my hands on some SPI asap......
SPI....It has several days window to re coat or top coat without scuffing and it sands beautifully. Used it on two cars and two engines, no issues. It even has UV protection for use as an exposed surface. My 6 pack hood is SPI black w/ flattening agent.Can't comment on SPI, have not used it , yet. In my beginning days I was advised to use PPG brand epoxy primers and since have tried two of the cheaper brands Mastercraft and Transtar, and PPG wins over them hands down. But will seek to get my hands on some SPI asap......
Guys, I admit I am self taught and know nothing other than what I learned from car mags and others who had experience with automotive paint. But, I have never thought about sanding epoxy primer. I normally use it over bare metal or rusty metal that i have clean and sanded best possible. I thought that is what you wanted, a good protective coat, why sand it off? I coat that with whatever type sanding primer I choose to use for that job. I also have thinned it and used it as a sealer, hhhhmmmmnnn, maybe I need to learn up.
Now in watching you tube vids, I see the guys who just do a fender or hood or door on a newer car do all different than the 50 year old clunkers I resurrect .