eastwood has a kit for doing just that..
http://www.eastwoodco.com/shopping/product/detailmain.jsp?itemID=2010&itemType=PRODUCT&RS=1&keyword=glass+scratches
http://www.eastwoodco.com/shopping/product/detailmain.jsp?itemID=2010&itemType=PRODUCT&RS=1&keyword=glass+scratches