I smoothed mine out on a knife sharpener wheel which is mounted on a bench grinder motor. It is a 10" diameter wheel made of compressed paper which is similar to wood in texture and hardness. It is loaded with jewelers rouge leaving a mirror finish.
The only reason that I even attempted doing this was twofold.
1) I had nothing to lose except useless rocker arms.
2) I could see that all that I had to do was look at the pattern of the grooves worn into the surface as a guide to maintain the correct arc on the surface.
I placed the rockers on the wheel and rocked them up and down to approximate what I felt was correct, checking it regularly to observe how the grooves were disappearing in an even pattern.
Jewelers rouge is super fine grit (if you can even call it grit), so it is slow going, but it gives you plenty of opportunity to do it right as you go along, constantly checking for the grooves to disappear evenly.
