Maybe it will be boring to some of you for me to post photos of the grille in another shade of gray, if so I apologize. In these photos it's been shot with several coats of high build primer. In the photo I posted this morning the darker gray was epoxy primer, which serves as a sealer, has very high adhesion properties, and makes a very good base for subsequent layers. High build primer, which is this lighter gray, is a high solids primer that builds thickness quickly and sands very easily. It (and the epoxy) are 2k (two-part) coatings, requiring a catalyst (epoxy) or a hardener (high build) in order for the coating to cure.
The goal of the high build is to fill any minor surface irregularities and sand very easily to provide a perfectly smooth surface for the application of the base color coat and clear. High build it not a substitute for bodywork and sanding to perfect the surface, I spent several hours hand sanding the grille before starting with the epoxy this morning even though the surface was very nice coming out of the mold.
High build needs to cure overnight so to be sanded well, so in the morning I'll lightly hand sand the grille with 220 grit sandpaper. At that point the surface should be extremely smooth and ready for the base color coats to be applied.
Sorry if I might have bored some of you with this but I'm often told that people appreciate me providing lots of detail on materials and techniques.