When I use to work for John Hughes Automotive Panel & Paint the rust prevention pack worked like this.
Customer paid for complete rust proofing, dealership only applied it to the areas where it would be seen.
Regarding this 'out of no where', coat they apply to the paint that 'once applied', negates the need for the car to ever be polished again.
This is the biggest scam of them all. As what ever they apply to it comes off when you wash it with water 'ask any detailer, any real detailer, how many chamois they've had to throw away because of this.
Best & Cheapest way to protect your vehicle:
- Apply a coat of quality wax to the paint work every now and then; and
- Go to Supercheap etc and purchase am spray can of fisholine, take the door trims off, the plugs underneath the sill panels, as well as the covers in the rear quarters and spray the crap out of insides.
Possibly best to do this on the grass as you'll get crap everywhere if you don't know what's going to drip where etc, leave the doors open and put ice cream containers underneath the drains, and let it dry.