Well I taught my horse to bow by using treats, but no ropes. We where just doing it for fun. I started with taking a carrot and pulling it down towards her knees so she brought her head down. Eventually I would bring the carrott between her legs and towards the ground, and if I had her legs in the correct position, when she brought herself down she would do a nice clean bow. It's probably not the best way to go about doing it, but hey. I was just teaching her for kicks and giggles.
A stubborn horse walks behind you, an impatient horse walks in front of you, but a noble companion walks beside you.