Technical Cant afford to paint yet Question

Paint Guru , I love all this information, and information is knowledge. Thanks Frank

 

I've used all three and find they sand great wet or dry.
I have an OT parts truck that's 2 years into life outdoors in the black. Time will tell when I decide to finish it but this was my personal test that's got a ways to go.
I'm not qualified to speak to the chemistry one way or another but encourage you to speak with the guy who answers their tech line.
It's his company I believe, and from personal experience will answer any questions.
Check it out.

As for quality SPI products was on 9 of the cars at the Pebble Beach Concours this year, including the grand prize winner.

 

I have used SPI epoxy .I like it.It sands good and doesn't gum up the paper.