This is how I did my Custom Grill for my Ralliart.
Materials and tools Needed (Dremel Tool, Sand Paper, Bondo, Paint of Choice w/ Clear coat)
Bondo
Sand Paper
Paint
Step 1. Use the Dremel tool to cut of vertical plastic grill.
Step 2. Apply and spread Bondo to the surface of the grill where plastic was cut off.
Step 3. Let the Bondo putty dry, then sand grill surface until the desired texture.
Step 4. Make sure surface if smooth.
Step 5. Paint the Grill.
Step 6. Sand Grill to take away excess paint.
Step 7. Paint grill again until desired Color and texture it met.
Step 8. Apply clear coat to Grill.
Finished Product
***** Sorry I was not able to take pictures of the mesh grill and how I cut it. It's not that hard to do if you have a dremel tool. *****
Peace and I hope this helps.