Try this.
I initially cleaned mine with one of these in an electric drill. The wire on this one was fairly soft, and I didn't go at it too hard so as not to scratch the inner lining of the pipes. Followed this up with a cloth buffing wheel coated with Solvol Autosol (liquid chrome cleaner) or somwething similar. Once you've got the heavy cr*p off, regular wiping down makes it much easier to keep clean.