Restoring a grill? repairs and paint?

I've had good luck using fiberglass resin for larger repairs. Make your repair piece out of plastic (even wood) then brush on the resin, it's strong, sandable and takes paint well. I've had very bad luck with cheap-o spray paint, but that could also be chalked up to poor prep.

To replicate bright trim on plastic (consoles, door panels, dash, etc.) you can get silver leaf and adhesive from any hobby store. use a rubber roller or stiff brush for the adhesive, let it tack up and stick the leaves with a soft brush. Burnish it with a soft cloth and shoot it with clear. Looks almost like a new chrome part.