You need a 600-800 grit scratch every where to gain mechanical adhesion. You can orbital sand or block/hand sand. For all of the edges and such I would follow with a Grey scuff pad. This ensures your product will stick. MOST paints have at least a 24 hour recoat window that you do not need mechanical scratches and can apply new material directly over the fresh paint and will gain chemical adhesion. Remember after the first coat of product everything sticks to the previous coat chemically.
