I think you are getting ahead of yourself a little bit. They aren't looking to you for guidance, they're running around to get away from the pressure. Step back a bit, and start with just making sure they are paying attention. Body language is key to round penning work - even more than it is on a lunge line. When you send them forward, you need to be stepping behind the shoulder, "pushing" with the shoulder that is away from the direction you want them to go while opening the door with the other shoulder by pulling it back. Basically, if you are tracking left you need to be behind the horse's left shoulder, your left shoulder should be back and your right shoulder forward and putting pressure on the horse. Probably about a 45 degree angle with your horses.
Then, work on stopping them by stepping in front of their shoulder and changing the direction of your shoulders. Turn your left shoulder in to shut the door. If the horse doesn't stop based on your motion - he's not effectively listening to you. Once you can do that you can add the step back and point the other direction (your shoulders are already in the right position) to ask them to move the other way.
It becomes a dance ... and it's very enjoyable. Horses are more in tune with body language and energy than you might think - I can even do this with my nearly fully blind horse.
Yup. Don't need a whip. Don't need a rope. Don't even need to spend $600+dollars. Just a simple raising and lowering of your arms and stepping back or forward. It does become a dance and is a lot of fun. I can get my mare moving by simply pointing in the direction I want her to go. Waggle my finger and she will trot, waggle again and she will canter. It's a blast and it's fun to show to non-horsey people. They think it's majikal. Just play with your body language and watch his response. And have fun.