Well the Subaru had water spots on all of the windows and the outside mirrors. They wouldn't come off with just the normal Windex so I had to get the next best thing, glass cook top cleaner. I still have a lil grime to get along the edges but all of the water spots are gone.
I got it at Wal-Mart. $2.97 for the cleaner and $1.97 for the pads. Just let the pads and cleaner do the work. It will go on like wax. After a lil bit of rubbing it will start to harden and then take a paper town and "buff" off the extra paste. I then take some Windex and clean the window like normal.