I'm working on the rust beneath/behind the rear side windows of my 73 Super Beetle. There are 8-10 spots on each side of the car that are rusted through and range in size from 1/8" to about 1". I have cleaned all that out. Behind is some kind of foam that I'm assuming has wicked some moisture from inside the body to the outside, causing the rust and paint bubbling.
My thought is to get as much of that foam out and replace it with some other substance that won't wick the moisture through again, then do a standard patch on the holes, print, re-paint, etc. I do NOT want to take the body apart and work on the panel from the inside at this time (this is a daily driver, not a show car).
Any thoughts on this method, and/or a recommendation on a substance with which to replace the foam?