Like was said above the best way to move an aircraft is with a towbar. However IMO opinion there is no harm in pushing or pulling on the prop as long as you hold the prop just outside the spinner. What is really bad however is moving the aircraft by pushing on the front of the cowl, especially Cessna singles as you will break the flexible cowl mount fixtures.
As always you should never turn a prop without making sure you will not be hurt if the engine were to fire.