After over 3 years cleaning windows both commercially and residentially, I can difinitively pinpoint optimal results to the following (3) criteria:  1)  The use of hard/sharp squeegee blades  2) Using a razor blade on windows when necessary to remove any excesss debris a strip washer won’t wash off  3)  Mixing Glass Gleam-3 with the water is the ultimate solution that won’t streak and will give tip to results.