The Dremmel 4000 is the most powerful rotary tool that Dremmel makes and is the best suited for fixing a scratch on your car. The Dremmel 4000 can be bought as part of a kit that comes with a felt and cloth polishing wheel. It also comes with a block of polishing compound, but you are better off buying automotive compounds from your local auto supply store. These compounds are specifically made for smoothing out the paint on your car without going too deep.
Wash your car with auto detergent. Auto detergent is specially designed to remove residue such as oil, wax and road dirt. It is important to start out with a clean, dry surface when repairing a scratch to avoid making additional scratches in the paint. Surface dirt can get caught between the polishing wheel and paint, for example, acting just like sandpaper.
Apply rubbing compound. Rubbing compound contains some grit that will smooth out the scratch. These compounds can be used by hand, but using the Dremmel 4000 will make the job go faster. Spread the rubbing compound over the scratched area. Use the felt wheel, since it is the coarser pad, and buff in a circular motion until the compound is dry.
Remove rubbing compound residue. Use a microfiber cloth for this step, since it is soft and will not scratch the paint. Rub in a circular motion and press down fairly hard. It takes a little elbow grease to get the rubbing compound completely off the paint.
Apply polishing compound. The rubbing compound leaves the surface hazy and dull. Polish brings the shine back to your paint. Again, spread the polish on the repaired area. Switch to the softer cloth wheel on the Dremmel 4000, working in circles until the area shines again.
Wax the area. Wax seals and protects the area you have repaired. You can do this step by hand. Use a microfiber cloth to remove the wax residue when you're done.
Rotary tools are not made to polish large areas like power buffers. Just keep this in mind when considering the size of the area you want to repair. For instance, if your whole hood is scratched, the rotary will not be your best bet. If you have a few scratches that are 3 or 4 inches long, the Dremmel 4000 should be able to handle the job. This technique is meant to remove scratches in your clear coat. If you can see primer or metal through the scratch, this technique will only make them less visible. Deep scratches often require a professional.