Re: WOW ... stop the rust while you can ...
I have two concerns.
1. The space is very tight and a spray can may not work - sloppy and may not cover completely.
2. Use a product that both neutralizes and covers to prevent future rust. If you are going to keep the car for a while you may need to reapply unless you use a quality product designed for this purpose. I applied mine with a flux brush after I masked the edges.