Try using any windextype spray,but first wipe Vigorously with a dbl page of newspaper; NYTimes,WSJ works better than USA,etc. The ink/newsprint combo seems to really cut that inital grime,imo. Follow w/spray cleaner and a good wad of bounty paper towels. I did my x5 that way,(the windows both in and out,had an amazingly stubborn grime on them),and I just did 60 huge windows in our new house with same "system" of newsprint first course. Good luck.md