When i was a beginner, this simple method of using my own legs, helped me develop a better feeling, squeeze, speed & understanding of “on/off” outside of class.
I still do it occasionally when I’m bored since you can feel the squeeze on your leg, you get a pretty good idea what you are doing, when and where the choke gets tighter, what difference a grip variation makes etc etc. Of course this doesn’t replace drilling and practice with a real partner. But it definitely can help a beginner to understand a choke better, do develope speed, to understand the squeeze. Drilling some chokes also made me faster. Whenever you are bored you can do a couple of reps in front of the tv, while warming up on open mat, hell, even when you are taking a bath haha