Use zxcv to change things, or scroll wheel, I use the scroll wheel.

I've always used good old fashioned clicks, in bursts of 1-3 dependent on what phase the joint is already in. I find it a lot faster and easier, as scrolls doesn't roll through the relax or hold phase of the joint.

This is my special move that ends up in uka or whoever is the opponet cut in half!
1#press C
-----
Then
left twist chest
make right hand grab
Contract elbow
hit space
then extend elbow!

It's mainly just practice. I have a 10 joint judo starter that i developed specifically for that purpose. Always practice, as I find move memory doesn't help when exploring joints, as i learned most toribash moves from failure. (But I'm still new what do I know xD)

If, even when using mouse wheel on the joints rather than clicking or keys, you still can't do moves fast enough then perhaps learn or develop less advanced/complex moves which you know you can complete in the reaction time. Just try to do the mouse movement and complete the move faster each game you play until you have time to add something else (another joint movement) to the move. Perhaps just simplify the youtube move you are trying to do and then build up to it.

With regard to how to build up your starter. My starter developed over a very long time and it works well for me while being rather unique so don't be afraid of starting out with an imperfect starter, just make sure you try to correct the problems it has. To apply this to building up to a youtube move: Just use trial and error to find which part of the move are most important to get done in the time you have, when you get faster do the same when choosing which joints to add.

Hope this helped.

Using the Z, X, C, and V keys works for me. Lets me use my left hand for moving, my thumb on my trackpad, and my fingers on the arrow keys for the camera. Much easier when you only need to push a button once or twice.

If you set the 'Mouse Buttons' option to 2 clicking your joints will only switch between hold and relax. I use this with the scroll wheel, this way I only use the mouse to move my joints

You just gotta figure out what you're going to do before its your turn. And you gotta be quick about the joints you click too.

Something some people may forget is that it has alot to do with how you understand your joints. If you know what your joints do you will know what to click and when, which makes you click even faster. If you need to think about what your joint is doing you will need to keep on working on your memory about where the joints are and what they do.

sorry for the drunk english, i just came home from skiing 6 hours straight.

Find a way to keep playing the game until you commit the controls and mouse sensitivity to muscle memory. There is no quick-fix, just ways to learn faster.