I tested a number of glass polishes a few years ago. The liquid polishes were fine for removing embedded road grime and surface crud but did very little to remove or reduce pitting and scratching. Most glass polishes are formulated to avoid damaging the glass.
I suggest using #0000 Super Fine steel wool when applying a glass polish. Good polishes are offered by Zaino, Duragloss, Detailers Pride (Autogeek), Einszett, Diamondite and a few others. They're very hard to find in stores as most of the major car wax mfrs do not offer a glass polish. Best thing to do is mail order.