Two different types of bending aids

In our last lesson, we worked on bending Duke with the reins.  Tonight we worked on bending him with my leg.  John said that with a horse like him who thinks, it is best to mix it up.
I was trotting around on a floppy rein to warm up, like John and Ashley said (or so I thought), but John got on and rode him and showed me (which was awesome).  Instead of letting him do whatever he wants, it was pushing him forward, even letting him run just a little bit, then using outside aids to firm him up, then using inside rein and leg to bend him, and then pushing forward again, and then the second pushing forward pushes him up and round into the reins, and he naturally goes up and over his back.  It was kind of amazing.  So John rode him and described it to me a few laps, then I got on, and it was cool.
And then we did canter, and I don't know why, but I am just struggling with any roundness in the canter.  As in, I can't even describe what John told me, even though he said it just as simply (and even more recently) than the trot aids.
It is sitting down, keeping seat moving, legs on and off, breaking up his neck, but the aids from my legs to my hands just defeat me.
From there, we did some jumping through a grid, which was a ground pole, cross rail, ground pole, vertical, ground pole, and eventually the cross rail and vertical became oxers that were cross rail/verticals, and then John put placer poles in the middle to make us go straight down the chute and not drift.  Duke was great - he just powered through although he likes to land on the left lead.  My big instruction was to look ahead through the turn, then put enough leg on to get us through, which was usually leg over the first fence and in between the first and second fence.
John said he likes Duke, that he's got a good head and tries hard.