Trying to fix 20 years of bad habits

Hey everyone. Hope stuff is going well for everyone as the holidays rapidly approach.

I took a couple weeks off riding (not on purpose) between a bad cold and then once that was over, the weather was crap. But Phoebe and I are still plugging away at stuff.

Lately I've been working on trying to fix the bad/ineffective habits I know of in my position. Phoebe's owner's saddle actually works pretty well for me, so I'm trying to take advantage of that. I am terrible about doing the "hunter perch". I think it's a combination of my hip structure and bad instruction when I was first starting to ride. So now I'm really focusing on pushing my hips forward to get rid of my hollow back and stretching my legs down long while also keeping my knees pointed straight forward instead of letting them roll open somewhat. It's hard to know if I'm getting it right or not without an instructor, but it looks ok in the mirror and Phoebe seems to go better that way, so we'll see.

Our routine now is to spend the first 10-15 minutes getting her to actually move forward off my leg with lots of walk/extended walk or walk/trot transitions. She has a motor on her but she likes to make you do the work if she can get away with it. Once a gentle bump produces a result I focus more on me. Last night we had some problems with our trot/canter transitions. She usually has issues with them which I can't figure out. What seemed to help somewhat was if I kept the aids on longer. I've never had a horse who I had to HOLD the canter aids on though. Most of them I can just bring my outside leg back, hold the inside leg steady, and give a bump with the outside leg and they pick it right up.

I don't suppose any of you out there have any additional suggestions? I'm not letting her run into the transition, so maybe she just doesn't have the hind-end strength right now to step into them in frame? I could just hold off on cantering for a month or two and see if that helps, but I like having the canter as a tool to help her think "forward". I find it hard to believe that she's not strong enough to step into the canter from a trot. I hate having to use the whip to make her go forward, but for the first couple of transitions it's usually the only option I've found that works.