The holds are not "extremely" taxing, I would say. The tremors can be induced through a simple 7 step sequence of holds like wall sits or calf raises. There are walkthroughs on YouTube.
On the TRE subreddit [0], people report being able to tremor at will once they have enough experience with the technique.
Not trying to be pedantic, just clarifying that it is very accessible! I've personally been experimenting with it and find it to be helpful.