Body filler is used for small repairs on the surface of a vehicle. It can fill dents and small holes and then be sanded smooth. This leaves a smooth, flawless surface for new paint to be applied. For a vehicle with many small dents in most of the surface, a skim coat of body filler may be the best option for finding and filling them all. A skim coat is applied to the entire car or at least an entire body panel and then removed to fill all of the dents. This is time consuming and should not be attempted by those with no experience.
Use the plastic squeegee to scoop out enough body filler for one panel -- about a small handful. Put the filler on the cardboard palette and squirt a nickel-sized amount of hardener onto it. Use the squeegee to mix, stir and blend the hardener with the filler. The end result should be a solid-colored mound of filler. If the color is darker in some areas, mix it more.
Apply the filler to the first body panel, using the squeegee to smooth it out. Use as little as possible to cover the panel. Let the filler dry while you mix more filler and move on to coat the next panel. Repeat these steps until all of the panels that you want to skim coat are coated.
Check to make sure the filler is completely dry before sanding. Damp filler cannot be properly sanded. Once the filler is dry, place 120-grit sand paper onto the long sanding block. Place the flat surface of the sanding block against the filler and keep the block smooth and flat.
Sand the filler in an X-shaped pattern until most of the filler is gone. Moving the sanding block in the same exact motion can leave high or low areas on the car. The X pattern knocks down these areas. Keep the block horizontal and use longer sides as the leading edges rather than the small ends, which could result in uneven areas. The remaining filler should be as flat as the surface of the car and fill any dents or dings in the car.
Use 220-grit sandpaper on the sanding block to sand the entire car again, using the same technique. This smooths the rough grooves left from the 120-grit paper. Once this is complete, the car can be sprayed with primer and then paint.
