I would prep them.
If i was you i would do the following on a DIY job but i am no sprayer but have done a few things in the past.
The grill is easy enough as you can remove it easy, mask off the Kemi badge unless you can remove it.
Wash the grill then dry and sand sand it with w&D 1200 grit just to key it, then wash it and dry it again with a clean lint free cloth. Then give is some good coats of primer let that go off then a good few coats of black / what ever colour you choose. I personaly like honda nighthawk black as it has some nice flake in it. then add a few coats of laquer jobs a good one.
I have never spayed mesh before so just becareful of edges etc sure if you take your time it should be fine.
Also because it is a grill i would have thought any small defects wont really show up.
The Lower grill may be hard to remove i know i had to destroy my old lower grill so may have to do it in situe which means really covering your car.
Hope this helps.
