Windshields are hard to repair, regardless of the problem. It takes patience and planning, a thorough understanding of the process involved and a realistic expectation of the outcome. Improvements can be definitely made, but returning damaged glass to like-new quality is highly unlikely. With that in mind, there are several processes that can be used to polish pitted glass. Severely abraded glass should be replaced.
Scrub the windshield with a nylon-bristle brush. Use a liquid dish soap. This will strip any oily residue from the glass and clean the pitted areas of any particles that have been trapped inside them. Rinse the glass with water.
Put on the safety glasses and gloves. Apply a commercial polishing compound to the glass and polish it using a variable speed drill set on low. Most compounds contain cerium oxide as an abrasive. This removes glass until the surrounding area is level with the pit. As the glass is being removed, some of it will begin to fill the pit and give a false impression that the pit is being repaired. To prevent this, continually flush the area by lightly squeezing a sponge that has been soaked with water to keep the compound damp.
Scrub the area with a brush and liquid dish soap again to remove the used compound and clean the pitted areas. Dry and inspect the polished area. Apply more compound and polish the area with the drill. Keep the area damp. Do not let the compound become dry, as that could cause unwanted scratches. Continually moisten the area with a small trickle of water from the sponge. Repeat this process until satisfactory results are achieved.
Clean the glass a final time and apply a rain-repellent formula available at auto parts stores. These fill in small surface imperfections, improve the overall appearance and add enhanced viability. They have the added benefit of repelling water and slowing windshield abrasion.