remove old flaky paint on the rim. Sand surface with sand paper. corseness of sanpaper depend on the condition of rim. Clean surface with soap and water. Dry rim. Mask area if u do not want surface to be painted. Buy spray paint of desired colour. Paint should be heat or chip resistant. Spray few layer, each layer as thin as posible. When finich painting color, remove masking tape. then clear coat the rim surface, if required
later when finish, stand back, admire your DIY with a can of beer in hand, provided u did not suffocate inhaling paint from the spray can. j/kidding....