Did you remove the grille from the full piece with the honeycomb/mesh part? As in, you only had the part with the two bars and logo to tend with? Just asking. All I used was cheap grey primer, 3 coats, and Dupli-color black, 3 coats, and put each coat on while the other was slightly tacky (5-10 minutes), which was after sanding the entire surface with 360 grit and wiping it with a tack/tacky cloth. The only issue is re-attaching the grille. I had to use 3m double-sided "tape". You can easily see the bolt that holds the logo on when you have it separated from the honeycomb/mesh part.
Mine's held up for over 8,000 miles/12,000 kms with barely any chipping, and it was chrome to begin with.
Edit - I also prepped and painted my fog bezels and chrome accent rings with the same process and color, which is holding up even better than the grille. I can't stand the flat black plastic crap.
Goodbye '09 SES. Hello '14 Titanium!