It's possible that teflon powder would loosen things up a bit but I think the main contributing factor is the very short moment arm at the rudder that resulted from keeping the cables inside the fuselage.  The stiffness was really a problem for me at first, not so much because it took a lot of force to move the rudder but because the force delta between no movement and a lot of movement is negligible.  This made me very reluctant to use rudder in the landing pattern, which is where it is most important.  With about 400 hrs. in Legacies, I have gotten used to it and am comfortable with rudder input.  Also, other than on t/o and landing, very little rudder is needed.  In fact, above 1000 ft, you can fly feet flat on the floor with no problem.