Sounds like your prop walk is to starboard when backing? In any event, when I teach this kind of thing, I have found that a number of people stall the rudder by either turning it too soon or too far, don't have enough momentum, or both. So you may want to try the following: try backing out of your slip with the rudder in the neutral position. As the boat makes way aft in a straightline, wait until the boat is about halfway out of the slip before beginning to turn the rudder in the desired direciton. As you practice this, you'll see you only really need to turn the rudder 10-15 degrees to move the stern where you want it. One of the key ideas here is to have enough momentum to gain steerage. Practice this with another crewperson (on a calm day)to help you fend off pilings or other boats until you get it right.