What do professional window washers use to clean windows outside without streaks?

the window washers at my husbands work, use a tiny amount of dish soap and water with one of those squeegy things. The dish soap really cuts through the dirt and grease.What do professional window washers use to clean windows outside without streaks?
white vinegar in the waterWhat do professional window washers use to clean windows outside without streaks?
Its the wiper/scraper thing that helps to prevent streaks
Dawn soap
a sqeegie
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skin care