Now that your horse trusts you and you have pushed them forward into the trot, how do you get them balanced? Let's be honest here, you will have to get them balanced because they won't just pick up a trot and do it on their own. This is where it comes to You stepping up and doing some work. Your inside rein is going to be for support, the outside rein is going to be your brakes and your voice and body is going to be your gas pedal. In the saddle, add in your legs as part of the gas pedal.
I like to use split reins when riding and when doing long line work I hold my lines much the same, bridged and running thu both hands so that I can easily slide my hands up or down the lines as needed. Working in the lines, I like to use the rings that are a bit lower and wider for the horse. When riding, I also try to keep my hands a little wider since a friend of mine pointed it out to me. Somewhere over the years, I developed the habit of riding with my hands practically ON the horses withers. On the withers and close together they did not move much away from that position for whatever reason. Her comment (praphrasing here) was to use my hands a little wider as if they were the sides of a channel in which the horses energy was flowing. Well that was when I was riding my WB mare Aruba. She was a BIG mare and needed a Wider channel for all of her energy. That made sense to me and when I widened my hands it made a big difference in her way of going. Same with the work in the lines, the reins are the sides of a channel to guide the horses energy. They need somewhere to move.
Once you have pushed the horse up into the trot, you will want to make contact using your inside rein. You want the horse to accept it that you are there for support with that rein and hold them slightly bent to the inside. When you want to slow them down or make adjustments, you will simply close your hand on the outside rein and if needed, make small tugs on that rein, letting them know that you're asking something of them. As they are moving, watch the ground for overstep and if there isn't any going on, you may need to push them up into the bridle using your voice and body positioning. Your hands will take a hold of the lines and stiffen slighty, giving the horse a 'barrier' of sorts and letting them know that this is where they need to soften and submit, breaking over at the poll and driving up into the bridle.
When they do this, You need to let them know that THIS is what you wanted them to do. Praise them loudly and make a big deal out of it. Use a happy voice since they can hear it in the tone of your words. When you get a few strides, let them relax little and then ask for a few more. Now that they heard you get excited and know what your asking of them, getting a few more strides will be a bit easier. Help them hold it as long as they can and praise them for it. Call it good on that side and change directions. Same exercise. Ask for forward movement and push them up into the bridle. When you get a few strides, praise them heavily, let them rest a little, do it again and call it a day.
There are a few other things to consider here and I will cover them in my next post, with pitures to illustrate for us 'visual' people.