My parents 2000 navigator is pretty rusty underneath. Can I slow this down? What I'm thinking is to spray the under side with something like picklex 20 then spray something like zero rust down there as much as I can? Basically I'll just put it up on jack stands and spray stuff down there as much as I can. I keep telling them the vehicles on the way out, but we could hopefully slow it down so they can get a few more decent years from the vehicle.