My first encounter with propeller issues:  I have a Hartzell Top Prop on my M20C that is 8 years old, has ~700 hrs on it, and has never needed major service in the 5 years I've own the plane.  Last November I noticed a little shiny streak on the back side of just one blade that was not greasy to touch.  I buffed it off, and it did not recur.  I mentioned the issue at annual in December and was told that they did not see any evidence of grease leaking from the hub.  Last week, I noticed the same