I work on this all the time. It's especially difficult at high cadence. I find the "scraping mud of of a boot" analogy works well. The main thing is just to learn to spin and stay supple and efficient.

THIS.

My left leg is noticeably weaker than my right. Don't know how it happened, but I'm working to try to fix it.

I do.

I ride mountain bike a little bit to focus on spinning circles.
I also do one-legged drills on the trainer. Just a few sessions of this and I feel immensely better when riding.
Trying to borrow a set of rollers from a friend for the off season for the purpose of working on and maintaining correct pedaling technique.

I've spent years working on pedaling technique! There's many different styles, all with their pro's and con's, and ideal positioning of saddle and pedal cleats within millimeters.

I've worked on creating an average steady cadence of 100-110 rpm with "high-heel" foot positioning, making a more even effort through my whole pedal stroke instead of a focus on the forward->down. This is most efficient & comfortable with cleats and saddle positioned slightly forward, and perhaps the saddle a little higher.

If that were true someone should have been able to measure an improvement but I don't believe there is any research to support the benefits of an 'improved' pedaling technique.

One study, "Effect of Pedaling Technique on Mechanical Effectiveness and Efficiency in Cyclists" found efficiency was highest when riders just pedaled with their preferred style. When they changed pedaling technique to focus on a more even distribution of torque throughout the pedal stroke their efficiency went down.

A quote from the article:

I think that "styles" of pedaling is one of those baby boomer's science-ra-ra-we-can-engineer-our-body-to-be-better-than-natural things. Let your body sort itself out under pressure; that's what it's good at. Pro cyclists don't pedal in a "round" fashion; they mash, and they're silky smooth at it. Your legs are not good at applying power across the bottom and top of the pedal stroke: the geometry of the legs and muscles are all wrong. That's why oblong/non-round chainrings go in and out of fashion without apparent affect except to those people who try to out-think their bodies and screw up their tendons applying forces their legs aren't built to withstand. The non-round chainrings all act on the principle of changing the torque on the crank in the 12:00 position where the legs on a good cyclist aren't really doing anything anyway.

Get a decent fit; at least make sure your knees have the right extension at the bottom of the pedal stroke. Get some good pedals and halfway decent shoes so you aren't constantly thinking about where your feet are with respect to your pedals. Then ride a lot of miles at all sorts of pace and efforts. A lot of miles; like, 10k or more over a couple years. That's how you get an efficient pedal stroke.

Side note: rollers help you get a quiet upper body and a consistent pedal stroke so you aren't swinging your bike all around when you pedal. One leg drills help your legs evolve more even power. A "round" pedal stroke where you are applying power all around the circle is not something to strive for. Strive for a smooth recovery of your recovering leg and applying power in a forceful manner at the point where your legs can get force to the pedal at its most efficient angle. Pros don't have a round pedal stroke, they mash, and trying to do stuff like ankling or pulling has caused a lot of bent up tendons for a lot of riders.