My understanding of having your outside leg back is to "push" the rear end over to get the correct lead. Then you ask for the canter with the inside leg.
I know English is different than Western and I'm not that familiar with English. In Western, or at least the way I ride, I don't do anything with the reins. Also, I don't keep leg on as Velvet suggested. The horse should be responsible enough for it's own feet to stay at the same speed, but that has to be taught to them.