Assuming you are buying the Porter Cable... Removing a scratch requires you to remove the layer of paint or clear coat that contains the defect. This is best accomplished by compounding and polishing with a circular polisher (Makita 9227, Dewalt 849).

That said, minor scratches can be easily removed with a dual-action polisher like the Porter Cable 7424 and deeper scratches can be made much less noticeable. The procedure requires spot compounding with a wool pad, spot polishing with a foam pad and finishing with your favorite wax or paint sealant. Compounding abrades away the area surrounding the scratch to the lowest point of the scratch. This makes the scratch invisible. Polishing fills any trace of the scratch and restores surface gloss. Finishing protects the surface with your favorite wax or sealant. These are the same three steps used by automakers, detailers and body shop technicians.... http://www.properautocare.com/witporcabpol.html