If you in Canada, I would recommend staying away from Final Coat CM2000 module; it has nothing proved that this "electronic" solution works. It's beyond physics laws and common sense. The same probably about other models.
If the car is brand new, it goes through a treatment that effectively makes it rust proof for about 7-10 years. The rust proofing offered by various dealers and companies is largely a gimmick, designed to make a quick buck, sorta like the extended warranty you can by at most electronics shops.
Look at my own investigation in this article