I agree with kevinshorses that there is definitely a "right way" and a "wrong way" to do the rope wiggle. I've never been able to get consistent, happy-faced reactions from my horses to the rope wiggle method, myself, but I have seen it work beautifully, and have backed horses that way myself. My boys must just be dense...
For a horse without a clue about backing up, I put my hand closest to them on the bridge of their nose, about where the noseband sits on their halter, and put gentle pressure there and make a clucky "we're moving now" noise. The noise says move your feet, the pressure says "not forward this time." Make sure you are standing facing their shoulder, with your feet at a 45 degree angle to their front leg (in the "safety zone").
When they have it really nice that way, I'll graduate them to me just clucking while I'm facing their shoulder. If the idea doesn't carry over, I remind them, either with hand pressure or by picking up on the lead (this is why you want to initially start with your hand where the noseband sits, building a "reverse button") and gently guiding them back.
Hope that was helpful, good luck!