Question about sealer

If you want to spray an epoxy sealer over your surfacer (paint isn't going down for awhile) you can, and then 600 wet sand the sealer prior to shooting, I've done this as funds don't always allow jumping straight to the paint booth and you need to seal the surfacer as it can absorb moisture/contaminants. I've heard said what's the diff - epoxy sealer over cured surfacer vs paint over cured sealer ? Don't know but I'd prefer a chemical bond over mechanical any day (eliminates some of the human error ). I've done both, so far no paint job blowing off at highway speed. Number one as said - stick with a system - Nason's decent, but coverage with their base can be ridiculous - that sublime over grey sealer on my car - gallon and a half(that's unreduced and does NOT include trunk/jambs!), maybe 5-6 passes - they just don't use alot of pigments, which is what you pay for. There's plenty of awesome Nason paint jobs out there tho.