something i’ve found helps me a lot is taking notes on manuals. you end up spending more time ingesting the concepts which helps them stick, and putting things in your own words keeps you from glossing over something that maybe you read but didn’t fully take in.
i also only take notes on things that don’t work the way i naturally assume them to. if playing the thing by intuition got me there already then i already “knew” it before going through the manual. this keeps the notes useful and quick if i need to refer back to them.
doing it with pen and paper is also great because you can easily give things different emphases by the size of your writing or by circling things or creating different layouts, you can draw the icons/buttons/whatever you’re making notes on, and it’s slower than typing which goes back to my first point.
and something i got from learning traditional instruments - doing a little bit every day over a few weeks will cement things more than doing longer sessions that are spaced out by even a few days. of course, you can’t top daily long sessions. 