Get any clay bar kit. Buy some Windex. Wash car. Spray window cleaner on the car and clay bar it. Keep it wet and lubes as you skim the paint.

Once it gets dirty retire it to using it on the glass. After about a year/season. After that glass use for a year, retire it to the wheels. Eventually you'll have 3 clay bars in some state of cleanliness. Paint, Glass, Wheels.