Many compounds are on the market for filling small holes, dents, and creases in the surface of your car. Most kits contain at least two substances: the filler and a hardener that you mix with the filler before you use it. Check carefully at the auto supply store to find the kit with the easiest instructions that can do the job for you as simply as possible.

To give you an idea of how to apply body filler, here are a few general instructions that suit most situations (but be sure to read and follow the directions on the product you buy):

1. Clean the body area thoroughly.

   Remove all traces of dirt, wax, and rust.

2. Sand the area.

   Use #180 or #220 aluminum oxide sandpaper or the type specified for your vehicle’s plastic or aluminum parts.

   The salespeople at the auto supply or auto paint store can help you make the right selection. Because body fillers don’t stick to paint, you must sand the area. When sanding, be sure to feather-edge (blend) the paint edges to prevent the old paint from chipping up through the new paint in the future and to ensure a good bond. Gently work inward from the edges of the dent to avoid enlarging the damaged area.

3. Mix only as much hardener-filler as you’re going to use right away.

4. If you're patching a hole, place something beneath the hole to keep the filler in place.

   • For a hole in the metal part of the body: Put fiberglass screening or fine aluminum chicken wire beneath the hole (on the underside of the body).

   • For a fiberglass or plastic part: Use the appropriate patch kit available at your local auto supply or auto paint store.

   Be sure to clean the area under the edges of the hole thoroughly to get rid of any dirt or paint. Then mix a very small proportion of filler and hardener and apply it to the edges of the screen and the edges of the area to be patched in order to hold the screen in place. If the kit contains no applicator, use a putty knife or plastic pot scraper to apply the filler. Let the screen patch dry for several hours before moving on to the next step.

5. Apply the filler.

   Work slowly and carefully to avoid spreading the filler outside the dent or hole and marring the surrounding area. After you finish, the filled portion should be slightly higher than the surface of the car around it.

6. As soon as the filler starts to harden (about to the consistency of hard cheese), use a perforated file to bring the level down almost to the level of the paint.

7. Wait at least 20 to 30 minutes until everything is bone dry; then sand the area with medium-grain sandpaper until it conforms perfectly to the surrounding body surface.

8. When everything is smooth and even, prime the area and touch up the paint.

   You can use primer as a last layer of filler to fill tiny holes or irregularities. Apply several layers of primer, sanding each layer with a sanding block, until the area appears perfectly smooth. (To check that it’s smooth, wet the primer and look at the way light reflects off the surface.

 

Source: dummies.com