I have always scuffed and epoxy prime ( or sealer as I and other like to call it) and paint. Anytime I do not know what the product is made from I will use DP40 epoxy primer first. I have been using PPG products for close to 25 years and my father has been using them for longer than that. Any issues I have had have been from me and not the product!
Scuff. Prime. Paint. Done. Move on to something else!
