Totally Bare for Epoxy Primer?

Hi all, I need the expert's help. I last did body work in father's shop around 1976! Driver fender off a '75 Scamp/Brougham. I had a little surface rust on back side so I got to bare metal, cleaned it up and hit it with POR15. This will never be a show car, but I love trying to make it better. My question is, can I use a spray can of "2K Aero Epoxy primer" I've had laying around from Eastwood for a couple of years? I'm not down to bare metal everywhere on this back side, maybe 60%. I'm down to primer everywhere, I'm just tired of scraping, grinding and sanding on the back side with the limited tools I have. I want to get to the side that counts. Should I keep going? I am going to undercoat it before it goes back on the car.
Driver's fender (14).jpg Driver's fender (15).jpg