This going to sound strange but you have to take my word for it because it works...
Get some really fine steel wool (just home grade stuff not industrial or anything) make sure that it is the most fine stuff you can buy, go to a decent auto shop and see if they have "Glass Polish" - it looks just like normal paint polish but its made specifically for glass, Meguires, Auto Smart, Mothers and Turtle Wax all make it.
Put the car in the sun and apply the polish with the steel wool, making sure to scrub every single square milimetre of ths glass (dont apply to much pressure or you will scratch the glass) keep the steel wool moist with polish at all times or you will scratch the glass...
Leave the polish to dry, then wipe off with a damp clean cotton rag (old bed sheets are perfect) DONT USE NEWSPAPER!
Repeat this until all of the marks are gone... WEAR GLOVES because it gets in to your hands, dries them out and your skin will crack and be sore for weeks.
Finish off with some spray on glass cleaner and a clean cotton rag.
I have used this techique literally hundreds of times (when I was a detailer), it works.
Good luck