You can make your own glass scratch filler from common materials like polishing compound, also known as jeweler’s rouge. When applied in a circular motion with a buffing pad, this is quite effective for filling small but visible scratches. After applying to bigger scratches, you can polish them more, preferably with an electric buffer. Once the polishing is done, wipe the glass surface with a solution of 2 parts water with 2 parts ammonia. Remember to wear gloves and safety goggles while using chemicals like the ammonia solution or electric tools like the buffer.