Draw reins with John

I had a dressage lesson with John today and it was amazing.  I told him how Charlie felt all bouncy from the hock injections, but I never noticed it before.  He said it's because I never rode him engaged before, so I couldn't tell.  He said to feel for when it peaks, and then figure out how long it was between the injections and the peak, and then get his hocks injected that many weeks before a three day.
Then he explained the difference between a collected canter, and a working canter with some lift - he said even for advanced horses, a collected canter is very difficult to do.
The first eureka moment was when he told me how Charlie was tilting his head to the right (we were going left, counterclockwise) and said that when Charlie does that - i.e. when I can't see his jaw but only his eyelashes - to lift up with my left hand.  That straightens Charlie's face out and doesn't let him evade the bend.  But then he tries to evade other ways, so I have to keep my leg on and keep him going - I had to use the whip.
Then John put on the draw reins.  I haven't used draw reins sinceWillig, so there was an incredibly horrible period where I couldn't figure out how to get them in my left hand, but then I gripped like there was no tomorrow so we wouldn't have to go through that again.
It was AMAZING.  All of a sudden, Charlie's shoulders were lifted, and I didn't have to fight with him, and it was just divine.  We worked on 20 meter circles, 15 meter circles, 10 meter circles, leg yield, and trot and canter. Our first canter was like that eureka heavenly moment with Mike - the sky opened up and angels sang and I was just riding on a cloud on top of Charlie's back.  It was amazing.
At the 10 meter circle, Charlie tried to get out of work again, and so I had to sit tall, and then put my butt down on him, and then use my hips to swing him up and forward (and leg and whip, of course), but I had to really keep him going.
John said I can use the draw reins by myself sometimes, but not all the time, because I am extremely unlikely to ever ride with them too short (he had to keep telling me to shorten them - again - again - again), and that is their risk.
Charlie's butt was so sweaty afterwards!  Even though I sponged him off, when we got back to the barn, he had that caked on sweat look and needed to be curried.
John also showed me a ground exercise for Charlie's topline.  He said that Charlie has never been a muscley horse through the topline, and that he is on the skinny side right now.  He showed me how to squeeze just behind his hunter's bump and at the same time push up under his ribs.  He said to get him to round up, hold it a few seconds, and then let him relax.