sandblaster or wire brush + rust neutralizer?

RedFish - Thanks for reminding me that I need to fix the leak. That raises a comment and another question. It is possible that I have some leakage around the windshield that should be taken care of when the car is painted (windshield will be pulled and new gaskets used when put back). However, my bet is that the leak is coming from the air vent passage where leaves collected and possibly corroded the metal. This is probably a common experience - but the car has vents just in front of the windshield that allow leaves to pass thru and there's no way for them to get out. I've cut some ugly holes in the firewall to remove the leaves, but I'm thinking that I need to cut some larger and uglier holes to gain access to the surface around the circular vents so I can repair any rust damage.

Any experience to share on doing this?