Ignoring the adage "practice makes perfect", it helps to identify why you aren't executing the techniques correctly. Let's take extended dashes, and I'll assume hyper/wavedashes for this example. If you're not getting your dash back, you're probably pressing jump too quickly. 99% of the time, the spot you choose to hyper/wavedash should be suitable to be extended. Similarly, for wall bounces, if you're not actually getting the bounce part, you're a little too far from the wall OR you pressed jump too late and you're getting a normal wall jump. I'd offer a little more precise advice (assuming I know exactly why, as I don't know everything yet), if you had any footage of your practice. Regardless, figuring out WHY you're not getting the tech right goes a long way to fixing it up.

I'd recommend for practice with general movement, you go to the Awake section of chapter 2, and practice there. Pretty much no way of dying there, and plenty of open space to mess around.

Also, I wouldn't exactly know which any% runs you watch, but doing a test run and watching someone with a similar time (and ideally similar skill level) would be useful to learn from.

Before recording actual runs for Celeste Any%, I was curious if it is considered legal to switch controllers in between chapters. And it isn't just "one controller to the another controller of the exact same type."

For context, I am currently running the Switch version of the game with Joycons, and I also have access to a Boxx controller, which acts very similarly to a keyboard that can be connected to the Switch. What I want to do is run the game with the Boxx Controller until Chapter 6, and finish the run with Joy Cons.

If it turns out that this is deemed illegal, then I'll probably stick with Joy Cons for the run.