Update:

I glued the valves to 3/8" dowels with thick CA and used Mother's Aluminum Polish. Mother's is a very mild abrasive. The dowels made it easy to rotate the valves on the seats. When I was finished, I cut the dowels off, leaving about 1/2" then soaked the valves in acetone for about 10 minutes. That softened the CA which was then easy to remove. The YS runs great now!