Here's a little video on me using the water fed pole window cleaning system. In the video, I had to polish up the window using superfine (grade 0000) brass wool pad. Unlike steel wool, brass wool doesn't rust or degrade as quickly.
Using the 0000 grade wool, whether brass or steel, removes all those insect marks, minor paint marks, hard water marks and other such marks. If the marks are tougher, then out comes the scraper. But, thankfully, I didn't have to use the scraper.
Oh, you can see my "solar panel." :)