How to scuff up epoxy primer in order to spray the top coat?

Not sure ok n the brand you have but PPG says after the open time for chemical adhesion to ride so you can have mechanical adhesion. This is on the tech sheets. Thet say or used to n It th sand so we always used red 3-M pads. Then shot Evercoat sandable primer. My Favorite is Slick Sand.
I went overboard and shot it with 2 coats sanded, shot 2 more coats and wet sanded with 400.
Shot R-M Diamont Base and clear.
Was not to bad as a friend and I passed the gun to each other as we shared the job. As it was quite a long job to shoot it on jack stands

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