I'm not sure what 'epoxy' is anymore. Epoxy used to appy to anything that comes in two parts that needed to be mixed together. Later, epoxy was seperated from polyesters (two part resins). Now I'm seeing epoxy as an air dry product.
Epoxies were originally developed as glues and don't have any problems sticking to most surfaces.
I work for 7 BenMoore stores but not as a painter, you may want to check on the primer. Technically speaking, you shouldn't need any and it could foul things up.
Pro knows his stuff and I'm guessing that he is correct. I'm putting this on my To Do list out of my own curosity.