http://www.ziebart.com/rust_protection/
About 15 years ago, a few guys I knew did the process at the local Chevy dealer. Same principle, they sprayed underneath the car, in the wheel wells, etc. They also drilled small holes and forced it in hard to get areas, then put a plug in the hole. It's not so common around here anymore, the economy doesn't leave much for extras when buying a new vehicle.