About to spray my car down with some flat black (not rattle can, i'm doing it right ). I want it to be super smooth, what would wetsanding and buffing do to it? I wouldn't mind a little luster, but i still want the flatness/satin look.

 

You can wetsand and buff it. If you are doing it the right way, you will shoot a flat clear on it. I know PPG sells this stuff and sure every other company will too.

 

satan finish clearcoat(aka matte/non glossy clear)

 

The right way aside from the clear.

I've had kinda of bad results with flat clear in the past.