Matt, DavidB a while back posted an idea that I use now for clay.
Cut half a bar into peices equal to the number of panels on your car. Use one peice per panel and then throw it away.
I don't like the normal folding method they post on the box. Your not getting rid of the
grime you picked up, your just hiding it somewhere in the clay, you never know if you are not hiding it 100 %.