Hi-Tech/Superformance comes through again. Good product support (before the fact, in this case) that inspires confidence that we will be buying (or have bought) a quality item that will be supported with necessary information.
The approach I used rust-proofing production cars was to get the car up on jack stands, crawl under it and locate openings and orifices in the underbody and lower half of the sides leading to interior cavities. Having done, so I would stick the application wand up into said interior cavity (including the interiors of doors, etc.) and blast the rust-proofing medium onto all the surfaces of the cavity. Production cars, designed and developed with longevity in mind, have a minimum of potentially problematic openings and interior orifices that might trap water, especially in the vicinity of the wheel wells where lots of water gets thrown during wet driving, so you are wise to try to locate all such interior cavities in the GT40's design.
The approach I used rust-proofing production cars was to get the car up on jack stands, crawl under it and locate openings and orifices in the underbody and lower half of the sides leading to interior cavities. Having done, so I would stick the application wand up into said interior cavity (including the interiors of doors, etc.) and blast the rust-proofing medium onto all the surfaces of the cavity. Production cars, designed and developed with longevity in mind, have a minimum of potentially problematic openings and interior orifices that might trap water, especially in the vicinity of the wheel wells where lots of water gets thrown during wet driving, so you are wise to try to locate all such interior cavities in the GT40's design.