Sometime simpler is better. I've tried a number of window cleaning products after a wash/detail and have finally decided on this basic technique: I use a foam gun to wash the car. Now, I foam up the windows, wash with my mit then dry with my waffle towel. Guess what - No streaks and the windows are as clean and look as good if not better then when I went through the whole process of using product on the windows after the rest of the car was dried off. I will still use product in bewteen washes if necessary but on my routine Saturday washes I'm back to basics.