Bearing damping (viscous friction that creates a force opposing the spinning of the bearing shaft) would be applied to the Internal Mechanics of the Rz primitive.
With "bearing stiffness and damping" together, perhaps you mean that the shaft can translate within the plane of the bearing. If that is the case, you should use a Planar Joint, and apply stiffness and damping along the Px and Py axes.
--Steve
