I have rust bubbles on the car and would like some advice on repairs. My concern is that the bubbles are the tip of the iceberg. I would also like to know what the preferred rust stopper product and what is the best method to reach areas you can’t see or access without tearing the car apart. Thanks Mike

...got a pic of the infected area??

Mine had rust bubbles as well and I originally thought it was on the surface. After media blasting we found the metal so thin that the media blasting blew huge holes in the metal. It's good that we found it. Here is an example....
Click to view attachment

mine had the bubbles too....but wasn't as horrible. Just needed a little fill.
...so all could be well....
(not the best pic)

I don't have a digital camera, but I will barrow one. The second part of my post was Does anyone know what the preferred rust stopper product and what is the best method to reach areas you can’t see or access.

Too early to say. Lets see pictures first. You may need to replace the metal that is rust damaged in which case you may not need any snake oil.

POR 15 is a good product line.