Hi Bill
we don't clean windows either but we have this problem all the time on builders cleans, get the ladders out mate, brand new blade in scraper, as you will know never scrape dry glass, the method we use which seems to be the quickest is spray a window cleaning solution onto the glass, then in a bucket we have hot water, washing up liquid and a bit of neat de-greaser, the washing up liquid makes the surface greasy and removes the paint easier.
MCM