I bought some large ball bearings in different sizes, then chose the one that fitted best, put it in place on the pivot, supported the brake underneath, then whacked it with a large hammer. I've since bought a hydraulic press which would have done a much more elegant job, but the hammer and ball bearing did the job.
With the stiffening kit, new springs, adjustment of the lever angle, RGM high friction brake shoes and new cable my drum brake seems to give about the same retardation as a modern disc brake. Well, at the speeds I ride it does. Together these changes made a huge difference.