Improper washing techniques will scratch and mar the surface of your vehicle regardless of whether you have a ceramic coating. The two-bucket method still applies. Clean rags, back and forth motions, lots of lubrication, and little to no pressure will keep the finish swirl-free. Mechanical ones use hard brushes, which can scratch the paint.
The quickest way to ruin any ceramic coated vehicle is to take it to one of those drive through car washes – especially if it has brushes or those curtain-looking mop-type cleaning rags. These car washes can wreck a ceramic coating in a matter of seconds.