The wear and tear of use causes the finest of any grill to deteriorate but not all grills need to be repainted. Stainless steel grills and enamel coated grills donâ€™t need it. A good hard cleaning might just be the only thing needed.
Black painted grills are subject to oxidation that gives the grill a dull, ashy look. You can first try using kitchen detergent and warm water to wash it, being careful not to use anything too abrasive or repainting will really be required. Lightly coat the affected areas with cooking oil after drying. This should restore the appearance of your grill.
If repainting is the only option, use only heat resistant paint specifically made for grills. The grill should be thoroughly cleaned and gone ever with sand paper. Opt for a couple of thin coats instead of one heavy coat but let the paint dry completely between coats. Fire up your grill to a high temperature once painting is done and completely dry to cure the paint.