I tried this after I saw the Thread as well. I started out with just a 4x4 inch piece and began using it flat but it tore fairly quick so ended up doubling over a couple times. Eventually I wrapped the foil inside a small piece of leather I normally use to polish and that worked much better as, even when crumpled up, it held and made contact well under the leather.

The razor I'm working on is a WB etched with "Special" on the blade and even working on the deeper rust and water stains around the etching it did not affect it. Definitely slow and makes a heck of a mess with tons of tiny little pieces of foil all over but it did seem effective and faster than Flitz and getting rid of bigger rust spots.

I definitely need to get more practice in with sandpaper but not long ago I grabbed a small piece of 100 grit that I though was 1000, seeing just the zeros on the back and not taking my time, then gave it a few swipes and gouged the metal deeply. So, still bummed enough about that experience I'm way more interested in trying different, slower and less aggressive methods even if it costs me time and Carpal Tunnel.