4. The process of applying flat clear is sort of similar to repainting a vehicle. The first step is to carefully and painstakingly sand the factory finish. Body tech Trevor Peterson used Keystone Automotive-sourced 2000-grit 3M sandpaper on a DA. This sanding gives the new finish something to adhere to. The trick is to sand the factory finish without sanding too deep, which will screw up the factory finish and force a repaint.