Otto, no need to wire wheel the rockers. Dunking them in solvent should be fine. Or scrubbing with a toothbrush and brake clean.
The rockers are under nearly constant pressure against the bottom of the rocker shafts and that's where wear would occur without good lubrication. It sounds like you don't have that problem at least with one shaft.
With that cracked tube, it may have been lined up with the top half and gotten at least some oil up to the rockers. It doesn't take much to do an adequate job of lubing the rocker shafts.
Let me know on the fitting.
