1. Wrap a sheet of 80-grit sandpaper around a sanding block and sand the pitted area aggressively. You can use a power sander instead of sanding by hand, but it might remove too much material and weaken the metal. If the metal item is very heavy, you can likely sand with a power sander.. Sand the metal and hardened filler with a sanding block and 80-grit sandpaper, if necessary, and wipe off the dust with a dry rag. Sanding with coarse sandpaper is only necessary if you were unable to scrape off the excess filler evenly, which leaves ridges and bumps of filler on the metal.