We have used Ziebart for years on our Jeeps without a problem while living in Michigan. We keep our vehicles for longer than 5 years so that's why we made sure we rustproofed them. Is there a reason you don't recommend it?
It must be maintained for the life of the vehicle. I've seen the results of failure to maintain. It begins to lose flexibility, peel off or lift in patches. That creates an opening for salt infused water to get trapped between the layer of lifted material and the steel.
Fluid Film is effective, and it also must be touched up/reapplied seasonally. However, it is also lanolin based. It is made from sheep's wool. It's environmentally friendly and non toxic. Even after years of applications, it can be removed with a non toxic degreaser (think pressure washer and detergent). In my opinion, that makes the vehicle more appealing for resale to regions where road salt is not an issue.
"There's nothing better for the inside of a man than the outside of a Bronco" - John Bronco