The first step in fixing a deep scratch on a car is to apply a polishing compound. This will remove the clear coat on the exterior of the car. Next, it is important to ensure the paint color used will seamlessly match the automobile.
After removing the clear coat and finding an acceptable match to the car's paint, apply a primer to the deep scratch and allow it to set overnight. This will assist the paint in adhering to the car at the time of application.
The next day, sand down the area with 1,000-grit paper. This should be done cautiously, being careful to remove any excess paint or primer in and around the scratch. After the area is even and smooth, it should then be cleaned in preparation for painting.
Prior to painting, reapply a compound to the sanded area. This will restore shine. After allowing the compound to set, the spot can then be painted and left to dry. Once it is painted, it will need to be sanded down to level the area. This can be done with another sheet of 1,000-grit paper. Depending upon your preference, the paper can be wet or dry. For the best overall appearance, the final process should be repeated twice.
The necessary items for repairing a deep scratch can be purchased individually or in a scratch-repair kit. Kits and materials are available in auto parts specialty stores or automotive departments at select retailers.