If you've never came across this before then your definatley missing out. Claying your car is very easy, takes very little effort and removes pretty much every contaminant on your cars paint work. I've seen it remove tree sap, tar spots, light off spray, metal filings you name it. If your planning on giving your car a coat of wax then clay barring is an absolute must
Heres a Meguires Demo Video on just how easy it is to do