Sadly Feynman technique presupposes you're taking good notes. It is also extremely labour intensive compared to spaced repetition without noting - using direct

Sadly Feynman technique presupposes you're taking good notes. It is also extremely labour intensive compared to spaced repetition without noting - using direct material of similar or higher level, preferably different modality - passive, creative, vision, sound, kinesthetic. How do you note a movement? Or sound? You'll waste some time reading material you already know, but that is the essence of spaced repetition; the use of different modality makes it much more potent. This is what the SR tools don't get, or where you need to put in huge amounts of time building decks. Most of them pose passive problems. Even the simplest learning books have exercises which are supposed to engage active modality, on top of testing.