Technical Rust and model A windshield frame

So I had a small piece rusted out on my 31' Tudor windshield frame, it's on the bottom and part of the wind deflector section that's rusted out.

My question is, what's the best way to handle the surface rust that's under the deflector? I thought now would be a good time to tackle it seeing how I have a 5" long opening to work with before welding in a patch.

My best attack I see at this point is pour a bunch of POR15 under there and let it slosh around.

No I'm not going to cut all of the spot welds and remove it then weld it back on. So I'm looking for the best way to seal it.

Also something better than POR15 for this? Thanks guys !! A picture for you

 

Sandblast it. Dunk in paint after welding and grinding.

 

Yes but I want something under the rest of the deflector too. The deflector runs about the whole length of the bottom of the windshield frame.

It has about a 1/16" gap between the deflector and the lower windshield frame so the only option I see is something that's pourable and letting it run back and forth under it....


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Is,nt this where the mol***es bath advice comes in. Make a trough and line it with some old portable pool sheet.