First, clean before sanding. Removing wax, silicone, road film, and shop contamination prevents abrasives from driving residue into the surface. Use the cleaner specified for the substrate and coating system.
Second, identify the substrate. Bare steel, aluminum, fiberglass, rigid plastic, flexible plastic, existing OEM finish, and old refinish material can require different repair products and primers.
Third, build a deliberate sanding sequence. Each grit should remove the previous scratch pattern without creating unnecessary work. Use interface pads and hand blocks to preserve contours and body lines.
Fourth, inspect under controlled light and clean air. Pinholes, featheredge swelling, deep scratches, and trapped dust are easier to correct before sealer and color.
Finally, verify compatibility. Follow technical data sheets for mixing ratios, flash times, recoat windows, and required personal protective equipment. A few disciplined checks at preparation save far more time than correcting the finish later.