number001,
We use California water blades in our shops. They dont cause scratches. Dirt does. Its how the user uses the product.
I've tried rubbing an MF towel using more than the usual pressure and swirls were evident after the test. But using the same towel with just the right amount of pressure, swirls were not introduced.
I've seen people in carshows using California or microtex dusters in such a way that they seem like rags on a stick. Upon closer look, swirls were heavy on the car. I was not too sure though if the swirls weren't there prior to using the duster or were they duster induced.