I have never painted the grille, but I do work in a paint shop. Here's what I would do, but get a second opinion from someone who has painted this particular part before...
1. Mask off areas you don't want painted/primed.
2. Sand. Since the part is chrome finished, I would use a coarse paper like 60 to 80 grit on a DA (if at all possible). You might even use up to 240 grit for this.
3. Spray primer in even coat over grille. DO NOT load the primer on. If you put too much product on in one coat it will never dry and it will ruin your final paint job.
4. When finish is 'eggshell' texture, spray another light coat. Continue this proceedure until scratches are no longer visible through primer.
5. Cure in direct sunlight. Press your fingernail into the primer (LIGHTLY) if you think it's dry. There shouldn't be a mark.
6. WET sand with 600-800 grit paper until finish is ice-smooth. Keep water continuously on surface.
7. Spray paint over primer. Try using one good coat without running it. Repeat if you need to. Just be very patient!
8. Almost immediately spray the clear coat. PAY ATTENTION not to run this product!
9. Bake the grille in sunlight for a few hours.
10. NEXT DAY, wet sand dirt and debris out of the clear coat using 1500 to 2500 grit paper and a soft touch. Careful not to sand through clear coat.
11. Buff with a variable speed buffer @ 1500 RPM, until mirror-finish.
That's how we do it on BMWs, Mercedes, and Lexus'. That's how I'd do it on my own car. Use the most expensive stuff you can buy and be very patient. GOOD LUCK!
