I've been practicing the octave tremelos (written as 64ths) In Lingua Mortua for three years. I've built them up gradually to at least 32's . I think I'm doing six per quarter note in the other hand. 64ths would be eight.I'm both rotating the wrist a little and wiggling fingers one and five, sounds like the advice above. Wrist is straight to the forearm. This speed of learning doesn't line up with the conservatories piece a month or whatever miracles they require of the students, but my progress is positive. So be patient, if I can do it, you can. I'm age 63. It takes a lot of strength, and while I don't slow down at the end, I do miss a few notes after I am tired. Take heart, if you get the strength to do this on Pathetique, you have the most difficult part of another piece down already.
(though I think your hand shouldn't shake much - it wastes valuable energy)
One approach is to start by playing the tremolos with 2 hands instead of 1. For example, let your left index finger play the bottom note of the tremolo and your right index finger play the top note. You should find it much easier than playing it with 1 hand. Play it several times, in tempo, until you have found a sound that you are happy with. After that you can go back to practising with your left hand.The rationale behind this approach is that once you have a clear picture in your mind of how you would like something to sound like, your brain will instruct your arms/hands/finger to play it so as to achieve that sound; you don't need to worry consciously about the precise details of how your left hand is moving to achieve that sound. In other words, according to this approach, all you need to know is "what" you want something to sound like, not "how" to achieve that with your arms/hands/fingers: once you have the "what", the "how" will take care of itself.I know this approach runs counter to the beliefs of many pianists/pedagogues. Just give it a try and see if it works for your. You can use it for any passages which present a technical problem. Start playing it with 2 hands.