[RaceAGMC]

You can start with some 400 grit sandpaper or maybe something a lil finer depending on how dull the grille is. Then step up to 800 wet, then 1000 wet and so on, you can go all the way to 1500-2000 wet, then you can hit it with some polishing compound and a polishing wheel on a drill. Beware: this will take HOURS to get the finish you are looking for, but it is worth it.