Also: I do not know the mix ratio chosen for use as a sealer for SPI in this scenario, many people use different ratios. which is fine, but the less reducer you use the longer it takes to cure. When I use it as a sealer, which almost ever job we do. I spray it 1:1:1, I apply only ONE coat, I treat it as a adhesion promoter, I am not trying to get full coverage, I don't need it with Motobase, it covers like ink. IF a true white undertone was required, spray one coat of white motobase down first over the ONE coat of sealer, not 3 coats of sealer. There is a big difference here. The adhesion weak link is always the base coat, therefore applying one thin coat of epoxy as a adhesion promoter makes me feel much safer against anything that may go wrong. I also mix it 1:1:1 because I know solvents escape much faster. this makes me feel safer against non compatibility issues as we have seen here.
Also when I stated when I do 3 coats of epoxy I let it sit for 3 weeks. yes, I do that however in that scenario it is not mixed as a sealer and it is sprayed with a larger tip than maybe even I should be using, however I wait 2-4 hours between coats, and we have found in the second week it may still leave residue on the sand paper and find it sands better after 3 weeks. BUT that is mixed 1:1 as a primer. Also a completely different scenario.