That is a nice find, and will be worth the work to try and get the paint off. Actually, I'd try Cellulose thinners under the bottom bracket to start with, see if it starts to remove the paint layer. You'll have to be careful though as the original top coat is probably lacquer.
Another way would be cutting or rubbing compound on a buffer. It would be worth buying a dremel, they have lots of small polishing wheels for tight areas. Good luck