Scribing (exacto knife, opposite the sharp edge) and diluted latex craft paint. I spend a fair amount of time scribing the door / tunk seams deeper knowing paint will partially fill them.
AMT 57 Chevy 1/43 came molded yellow. Filed down the hood bezels and front fender thingees. Sent the bumpers and headlights to Chrometech Bob. Stole the wheels from some die cast
Took an AMT Mustang II and kitbashed it with a 69 Shelby & 70Mustang Boss 429, Tamiya Gun Metal metallic & TS-13 clear in a spray can, Kieth Marks 68 Shelby Decals, Aoshima wheels, and some body putty.
Voila' - Mustang II Shelby GT500KR