I've used the Meguiars clay bar, it comes in a kit with the quick detailer spray and works quite well for light marks.
Although I would probably use Meguiars paint cleaner which is what I use for tar and bird crap, it's slightly more abrasive than the clay bar.
Also works better than Ultimate compound and cheaper :)
EDIT : Ensure after cleaning / prepping that you use a polish and protect the surface with a wax, otherwise your leaving the paint exposed and it will wear differently to the rest of the car.
I've used the Meguiars clay bar, it comes in a kit with the quick detailer spray and works quite well for light marks.
Although I would probably use Meguiars paint cleaner which is what I use for tar and bird crap, it's slightly more abrasive than the clay bar.
Also works better than Ultimate compound and cheaper :)
EDIT : Ensure after cleaning / prepping that you use a polish and protect the surface with a wax, otherwise your leaving the paint exposed and it will wear differently to the rest of the car.