That WAS a lot of information, and stuff that might be more comprehensible after working with the trainer, since it is built on top of more basic things. I think it will be so cool for yoiu to have a month of 1 to 1 training. I envy you.
What I would have said regarding slowing the trot down is to slow your posting down. I am assuming that you are posting the trot. (which maybe yo9u are not). YOu set the rythm that you want (that's reasonable for this horse's natural trot rythm) and you keep that rythm, no matter what the horse does. He will come back and match your trotting rythm.
AND, if you are sitting the trot, use the half halt, as the other said. (can use for trotting, cantering, anything , of course)
Here's my description of how your body will do this:
it all ties in with what the others said in that by slowing your body, the horse is forced to match you. In the beginning, you can reinforce this with the reins, but after the horse become sensitive to your body, you might not need to add any rein pressure at all.
The trick is that your body must have a clear difference between "going with the flow" and "restraining the flow". I think of restraining the flow as becoming heavy and firm. My body kind of solidifies from the knee up (do NOT press down hard in the stirrup and do NOT bring the lower leg forward). It is most focussed in making your pelvis and abdomen (core) firmer, almost ast if you are trying to push the horse behind it. The lower leg can lightly apply some pressure to the horse's abdomin to encourage him to step under himself , to NOT back away from you. So, you are kind of compressing him between the lower leg saying "step up, please" and the pelvis saying "just to this point, please". It helps to also firm up the muscles in your upper back. You want to bring your shoulder blades closer together . This is all part of making yourself STOP following his motion. The area right behind your armpit? You tighten that area, and bring your elbow back toward your firming core.
Lastly, you close your hands on the rein, and if the horse does not stop with this, then you close them like CONCRETE.
When horse stops,., reward.
NOW. That is what you do to halt. In order to slow, you do the same, but only for a stride or two, or until you get a perceptable change , then release. The horse will speed up , and you do it again.