When you guys mention scuffing the powder coating on rally wheels before painting them the correct GM argent silver what exactly do you mean? I am guessing it is because the silver paint won't adhere properly to the smooth powder coating? How much scuffing is just right and how much is too much? Would you use a fine grit sandpaper to do it? Thank you.
It will stick to the powder, but I wouldn't want to chance it flaking off in the future, and as I have seen the powder coated finish has a bit of a orange peel look to it, so sanding would also help remove some of that. So then when you spray the silver it will appear more natural or more factory correct than just the powder alone.
As far as "scuffing" powder is pretty hard stuff, I think 400 or even 300 would be fine. I would start with the inside of the wheel and try a couple test spots that won't be seen to get your desired sanding and spray it let it dry and see how you like the appearance.