What I was told about single stage is that they put the "clear " into the color and when it cures the clear rises to the top layer so you have to be careful not to cut/buff/polish because it's thin enough that it's easy to cut right through. I have never tried to polish a single stage so I'm curious as well. One of my cars has a single stage and the surface is not as smooth as I would like. It's a good paint job so I didn't want to screw it up but it would be nice to be able to smooth out the finish a bit and maybe make it shine a little better in the meantime. The guy that painted the car said if I thought it looked ok to just leave it alone.