Dave, if the "primer" you are using is an epoxy, they are usually pliable for 3-4 days after application. You could still run a panel thru the wheel to smooth it out and not affect the paint adherence.
I use this product...
https://www.southernpolyurethanes.com/epoxy-primer
This stuff is wonderful and could make Stevie Wonder look like a pro. I'm still at beginner level with painting and I can apply this to look good.
72-120 HOUR pot life in a sealed container. Can be reduced as a sealer only, although I don't do that.
Self leveling, as long as I don't apply to TOO thick.
7 DAY overcoat for seam sealer and color coats without sanding...
Yeah, the only product I use anymore for bare metal sealing/priming.
1 more thing about SPI, if you have ANY problems or questions about the products they sell, the owner, Barry, will answer his phone damn near 24/7 and walk you thru a solution... seriously. Where else would you get personal service like that ??