A good dollop of brush on rust eater may do if you've got rid of the thick 'n crusty stuff. A few sharp hammer taps sometimes shakes the crusty bits off too.
Oh it's been walloped within an inch of it's life. It's the annoying little pitted bits that remain that take time. Might try the rust-muncher that I have in the cellar on the more awkward areas.
Edited by Juju, 26 August 2008 - 03:10 PM.