Rust proofing your classic car

I've been doing this for years on all restorations that I have completed. I normally do this as the last step before the car leaves. I refer to it as cavity wax or cavity coater. I do the inside of frame rails, door seams, hood seams, and trunk seams. Basically anywhere there is an area where paint has a hard time reaching. I even do this on my new cars as soon as we purchase them. I will be finishing a 69 RR shortly and it will get the treatment.

Thanks
James