We did a project once that invlolved metal ceilings that were not decorative, but were not the easiest surface to scrape. We used compressed air through a nozzle made by my brother-in-law. It was an ingenious peice of Geraldic Engineering. There is a nozzle available that is used to blow away dust, the tip if this nozzle screws off. It's been so long that I don't really remember how he did it, but a piece of copper tubing attached on the nozzle and was supported by a dowel. Being flexible, it could be pointed in any direction and, with enough air pressure, was able to blow off most of the loose paint. the catch here is that the paint we were removing had no bond at all. So here's your dilema, there are a number of strippers available (someone here named "hy" seems to know alot about them) that may be the solution to your problem. Peel-away may be the answer as it is simple to use and makes removal from a sculped surface rather easy. The question I have for "hy" is, will it damage the tin?
Once your back to the metal your in business. Question here is, what do you intend to do with it? If you intend to repaint it, I'd reccomend using Brunning's "Grabber Plus" Primer. It's latex so it's easy to use, and it sticks like burnt rice to your wifes best cookware. This stuff is an adhesion primer, be carefull with it, what it is allowed to dry to, it will stick to for all eternity. After the primer is dry you can use just about anything to finish with, but I strongly reccomend using Benjamin Moore products.