I have used machine oil, cosmoline, and 3m cavity wax , formally known rust fighter, and the 3m applicator kit to get in doors and doglegs since the 80s, it works. I now use krown rustproofing oill inside and cavity wax on the underside, the reason being cavity wax lasts a long time, and can be removed with a hot water pressure washer. I think what you are looking at is about the same as krown, just figure out a way to get it everywhere and wash and reapply once a year and you are good to go. Our new cars always get krown dealer applied krown oil, only $160 to do a van. I think with the salt and beet juice mix they use here, along with car washes recycling water, it is the only thing that works short of not driving the car. It does make a mess for a while but...