Yeah, I really didn't understand the metaethics sequence the first time, but now consider it to be a clear and important section. The difference was in my own ability to understand. I think this is a good reason to do rereading rather than notes or flashcards.
I also experienced this and agree that one can't meaningfully memorize what one has yet to learn. I find that's an especially common mistake with flashcards.
My experience was that the Sequences, like most pieces of writing densely packed with information, cannot be understood on a first read-through.
Instead, following how memory works by association, the first time you read through them a little will stick, and the next time more, and so on.
To be slightly more clear:
I suggest that the first time you read through them, focus on the bigger picture. Don't worry about any particular piece you don't understand, just keep going until you finish it. A decent metaphor for this might be how buildings are constructed: during your first reading, you are laying the foundations and creating the skeleton of steel girders.
Your next read-through will help to flesh out more of the meat, and so on.
I stress that it's important to keep going; Rationality is long, and a slog the first time through. If you have to skip ahead, skip.
Hope that helps.
Restating stuff in different words is a good rationalist exercise, and "words used in empirical economics and psychology" is probably a better choice than most others.
Not sure how the language of empirical economics and psychology would help with the quantum physics, or even Bayesian equations, though.
There used to be recurrent Sequences readthroughs. Basically somebody would just post a link to the next entry in the Sequences and it would sit in Discussion for a week or so and be discussed. I found that re-reading them at a slow and deliberate pace really helped with absorption.
This spaced repetition deck was also somewhat useful, though I don't know if it was quite worth the time investment.
I have an Anki deck called Sequences - Useful Bits, where I threw some interesting things. Aside from that, re-reading is a good idea, as is talking with people who are familiar with the content.
I'm just beginning to go through Rationality: From AI to Zombies. I want to make the most of the lessons contained in the sequences. Usually when I read a book I simply take notes on what seems useful at the time, and a lot of it is forgotten a year later. Any thoughts on how best to internalize the lessons from the sequences?