I received a lot of good recommendations on materials for plugs for the Chinese Ball. Epoxy did not work exceptionally well, it seemed to be a bit brittle. The normal waxes that I tried had a tendency to soften if one allowed the cutter to become a bit warm as in harder woods.
The Seattle Chapter of AAW had a sawdust session in Jack McDaniel's shop last Saturday. Jack was showing me his new CNC lathe. I asked him if he knew where I could buy some machining wax, one of the waxes recommended. He said sure, but I'll give you some to try and gave me a couple of pieces he had used for tests. It looks like these plugs will do the trick. They do not soften easily, they machine beautifully, and they cast easily.
Thanks to all who offered opinions. If you are at Provo to attend the Utah Woodturning Symposium set in on my demonstration of making the Chinese Ball and you'll get to see those bright blue plugs I'll be using.
Fred Holder