I'd recommend using a sandable primer first, then use whatever paint you like (ie Krylon enamel, or automotive paints). Remember to use 3-4 thin coats, for durability. You shouldn't need a clearcoat. Be sure to mask off where you don't want paint (ie put some cheap screws in the standoff holes).
Painting the grills should be fine just take it very slow, apply a little paint let it stick and dry off a little then spray over a second coat. You never want to be at a point where paint is "dripping"