If you're painting the grille, Use Krylon Fusion spraypaint, but make sure you prep it good. Scuff it up real nice or it will chip easily. Let it set for a full 24 hours before exposing it to weather, including dew/dampness of the morning. I painted mine with that stuff, but I slacked on the prep work since I wasn't sure if I would like it. It came out real nice but it is chipping a little from bugs and pebbles since I didn't prep it real good. I'd say spend twice as much time sanding and cleaning as you do spraying and you'll be good. I have nothing for you on the bumper though. Maybe LineX with white XtraGuard, might look good, but probably not cheap. The local LineX shop quoted me $400 to spray my rockers and that didn't include the XtraGuard.
I've had real good results from the krylon paint on plastic when sanded and cleaned properly, without even using a primer. the painted grill is in my avatar. Black Krylon paint on the main part of the grill with Duplicolor Chrome finish paint on the honeycomb