How to Touch Up Your Car's Paint Job

By Deanna Sclar from Auto Repair For Dummies, 2nd Edition

Touching up a small scratch on your car with a little bottle of touch-up paint is easy. Before you start the job, mask the surrounding area well and use even, sweeping strokes to apply the paint. (Follow the directions on the can carefully.)

The techniques used to paint the body of a vehicle can vary depending on the size of the area you’re working on and the original paint and finish. Unless you have an experienced and steady hand (and the car’s original paint hasn’t faded or changed color since it was new), it’s almost impossible to conceal the fact that you repainted anything larger than a small area. Larger areas require spray-painting, which must be done in a well-ventilated area that’s free from dust and dirt. So if the area you need to paint is large, it will probably cost you less in time, money, and effort to have the job done by a professional who can match the paint and do the job right.

If you want a cheap but decent job that will last a year or so, find out where local car dealers take the used cars they get as trade-ins to have them spiffed up before resale. To save money, you can remove any rust, spot-fill, and paint the small areas yourself, and then have the rest of the job done professionally.

Practice on a piece of scrap metal before you tackle the car, and don’t expect the results to look terrific. Follow these steps:

Buy the right paint color.

Look on the firewall of your vehicle — you should see a little plate with the body number and paint code number on it.

Touch-up bottles of paint usually come with a brush or applicator in them. You also need a small bottle of primer unless the paint specifies that it isn’t required.
Make sure that the area is rust-free.

If the damage is only a deep scratch or a tiny spot, you may need just a dab of rust arrestor to stop the rust from continuing to form under the new paint.
Sand the spot carefully.

Use a small piece of #220 sandpaper to rough up the surface so that the primer adheres properly.
Wash the area thoroughly.

Remove any rust arrestor, dust, dirt, filler residue, and wax; then let the area dry completely before you apply the primer. Primer is used to seal a metal surface against rust and to provide a surface for the paint to adhere to. Primer also fills in tiny holes and imperfections in the surface.

If you’re dealing with a surface scratch or a chip that isn’t down to the bare metal, you can probably get away with simply applying the paint. But never apply paint to bare metal or plastic. If a bare spot is exposed, or if the spot is larger than a fraction of an inch, prime the area first.
Use a tiny brush or a matchstick to apply the primer sparingly.

You shouldn’t need more than a drop to cover the damaged area. Avoid getting primer on the original paint. If you do, wipe it off immediately. Let the primer dry thoroughly before moving on to the next step.
Mix the paint in the touch-up bottle.

Unless your vehicle is very new, the color probably won’t match exactly (which is another reason for keeping the area as small as possible). The paint on new models doesn’t fade as quickly or badly as old paints did.
Apply the paint, covering the surface of the spot completely and working inward from the edges.

If you’re painting a scratch or a very small area, you can cut down the brush or use a matchstick or toothpick instead. The paint should be no thicker than the surrounding surface or it will show, run, bubble, or peel off.
Wait several days for everything to dry completely.
Wax and polish the whole vehicle to blend in the painted area and bring everything to a high gloss.