Bob Geco sold me my water blade and I find it indispensable. I'm also partial to my Duster, but wouldn't dare use it on anything but a clean but dusty (and cool) car. Here in Manhattan, you seek out any effective shortcuts as it is very difficult to find a place to wash a car yourself. You're fortunate you have a light-colored SL, Ed. It won't show scratches easily. Your 911 is a different story, of course.