Just finished doing the same. Changed grey to black. Also did my 85 Camaro. I used the SEM vinyl dye/paint, along with their soap and Plastic adhesion promoter. Scrubbed the panels with the soap and Grey Scotchbright pads. Then wiped them with isopropyl alcohol. Sprayed them with adhesion promoter, let it flash off, 1 light coat of the paint, let it flash, then a med/wet coat. Then let them dry for a few days to cure. I tested a couple of pieces and you almost need a screwdriver to scratch them. Turned out well.