Bump... What if one doesn't want to spend all that time to sand every nook and cranny on the grill? Would sand blasting be too aggressive on the plastic. What about bead blasting or soda blasting? These methods, though more expensive,
would probably be more effective.
Would a self etching primer be needed on bare plastic?
Would an adhesion promoter and then a plastic specific paint be fine followed by a coat of clear?
I highly recommend that you sand lightly with 400, clean with a grease and wax remover (e.g. SEM 38373 or SemSolv 3837), and then paint it with SEM 39143 in satin (also comes in flat but it's really flat).
I have blacked out some fake "chrome" using this technique and it has worked really well.
SEM does not recommend a primer under their trim paint (SEM 39143) but maybe you could use some kind of self-etching primer instead of sanding. Maybe you could phone their tech dept. and ask.
I will be calling a specialty plating company today to get a quote on "Black" chroming my grill and headlight surrounds. I'm not sure how the black chrome will look, but I want more of a glossy finish as opposed to a matte finish.
Maybe I am being lazy and just don't want to do all that hand sanding.