^^^ that's decent advice. I recently painted my junkyard Barney purple Limited grill matte black.
Mine had lots of rock chips. Most of my prep was with a red Scotchbrite scuff pad, with some minor sanding with sandpaper. Lots of the rock chips are still visible, but that's fine with me for now. I did most of my prep and sanding in my driveway, wiped down with tack cloth, and spray painted in my front yard on sawhorses. Lots of light coats. Waited five days until installation.
One thing to possibly consider is painting the grille while in one piece, and not separated into the center piece and two end pieces. I painted mine as three pieces. My end pieces have slightly different paint appearance and texture, due to different prep/sanding and painting. Close enough for me, for the time being.
I considered painting mine to match my body color. I figured trying to match my 1996 green color via spray can might be difficult, and the color difference might look weird. Might try it in the future though. My junkyard grill was $17, so no big loss if I have to junk it for some reason.