Buy quality bar not cheap rubbish as it is all about the quarts crystal particles that are suspended in the clay. Whatever you do keep it very well lubed and work on small areas in straight lines following the shape of the panel. You don't need any pressure and check the clay for any debris and pinch out anything that you find.
As ever I'm more than happy to demo anytime at meets.
In itself it is not strictly an abrasive, think of it working more like a razor when you shave; likewise just as you can cut yourself shaving, you can damage your paint imam instant. Beware, be careful and check all the time.