This is what I've had great success with: P21S Total Auto Wash 1 Don't use it as an everyday wash but as a safe wax remover. It is better I think than the Dawn dishwashing liquid recommendation. This is also a good read on various products: Car Care Specialties, Inc. - Your Source For Quality Car Care Products, How-To Articles and Product Evaluations.

Claying is a potential solution when there is extreme overspray but it is an abrasive that takes a layer of paint off the car and I just don't like it unless it is really needed however some folks don't mind using it often so if this becomes the last resort do your research on technique.