Repair minor paint damage on your car before rust spreads and makes a difficult job. With a single-edge razor blade, cut away loose paint around the damaged area. Then scrape off loose rust, being careful not to let it slip into good paint. Clean with detergent and water to remove dirt and wax.
Apply a combination metal conditioner and primer to the area. Sold in auto parts stores, this product stops the rust, etches the metal, and primes it for touch-up painting.
If you can’t find the combination product, use a drill with a tapered grinding bit to remove rust. If all you have is sandpaper, mask the surrounding area with double layers of masking tape and work carefully to avoid sanding good paint. Wipe away sanding or grinding grit.
Apply a single-purpose metal conditioner; allow it to dry thoroughly; then with an artist’s brush, apply as even a coat of primer as possible. You must use primer; touch-up paint won’t adhere to bare metal. If you use spray-can primer, make a mask from a piece of cardboard, cutting a small hole in the center so that only the damaged area is exposed.
After the primer or combination product dries, apply the touch-up paint. Shake the jar to mix it, then use the brush in the cap to dab on the paint neatly.
If you can get a color match for your car only in a spray can, spray some paint into a paper cup; apply it with an artist’s brush.
Touch up wide scratches similarly, but don’t use sandpaper. If there’s rust, grind it off or use the combination product. Learn to live with hairline scratches; they may not rust for years. Touching up only makes them more noticeable.