I haven't done the grille on the Volt, but I've done 3 coats on other cars and it turned out just fine. 3 coats is a good base to protect against stone/salt chips as well. Depending on your area expect to recoat again in 2-3 years.

 

I used this product and it is holding up fine. http://www.armorall.com/products/custom-shield/?select=custom-shield
This time of year I use the automatic car washes to blast the bottom of the car.
I used two coats. It is now about 4 months old.


I have the white color and was going to do all the lower plastic parts but the arctic has sit in here.