If it is truly just surface rust, would wire brush off the flaky stuff then use naval jelly to neutralize the rust.
Then hit it with a wire-wheel and paint it with some good anti-rust spray paint

 

How about floor pans with a hole rusted through on driver floor. Hole is about the size of a lime. My carpet/rubber floor mat in that spot is holding nicely for the time being

 

That sound like pop rivets and small piece of sheet metal job to me. How we used to fix floors in old CJ's and the Jeep trucks from the 60's.

 

Anyone use this before? I'm thinking to undercoat with it and don't know if it's better than rust bullet or something else

 

It's a three year old thread. Let it rest in peace.

 

My bad, forgot to play my card

 

I prefer POR15 but I have used it and it works well. Being rubberized much depends on if you want to apply a top coat after using it. With this you basically can't which is perfectly fine if you don't want to. A black under body is pretty typical. With POR15 you can and if it's exposed to sunlight you should.

 

Thanks