[Zeke]

I've done my share of rust repair and it's imperative to remove ALL rust. The best way to do that in your situation is to spot sandblast. Hopefully you won't blow through. There is technique involved.

Once the rust is gone it's a simple matter of leveling the repair area and painting (which is another subject). Lots of YT vids on using spray can matched finishes and blending.

Some will tell you that you can encapsulate the rust with something on the order of POR 15. You can, but you still have to know the entire extent of the rust 'infection'. I won't guarantee the results using POR 15, but if it's only a utilitarian vehicle, let 'er rip.