Agree. We have had great results with SPI. Their tech info on the epoxy primer says you can only use Ospho as a rust treatment, if you need one, and we have done that with good results. We will continue sanding to bare metal, then Ospho, then SPI epoxy primer.
https://docs.wixstatic.com/ugd/8ced3e_b2286fdce9b249da92a7462b7c6af093.pdf
Also, when you call their tech line, you get the company owner.