Good morning all, there seems to be a lot of uncertainty about which products to use and how to go about applying them. this is to be expected given the amount of opinions and products available. the methods and products that i have suggested are what i have found work for me,but are certainly not the only solution.
There are so many variables to this topic,for example,is the car badly rusted to begin with,are the conditions right ie temp and moisture? how thorough do i want to be? how much do i want to spend? how much time have i got?
One thing i have found is that the box cavities are difficult, but not impossible to inspect prior to treatment, but this obviously would involve a camera,followed by finding a method of getting some vactan up there,followed by a long wait for it to take effect.
To achieve these sort of results,take a look at Phil Bates Kuro project,to give some idea of how thorough you could be, i really admire what he has achieved with his car,and would love to do the same one day ,but is probably, logistically ,beyond most of us.
The only advice i would give,and even this would be disputed by others,particularly companies who do this for a living come rain or shine, would be, only do this when the conditions are right,ie a scorching hot day,when all moisture has been driven from car, only after areas have been thoroughly cleaned and repaired[welded],and when you have enough time on your hands.
However,its not all doom, given the right conditions ,and all the stars align,i can say with some experience, that the whole underside of the car,inc box sections,can be easily done in about 30 mins,especially if a second person is on hand to pull out bungs to gain access ,and to remove wheels,liners etc. hope this helps,rob.