Without having to go into a summary of a memory course, one of the most important ways to learn is repetition. It's very easy to view courses once or twice, and then go on to something else and a couple of months later to have forgotten most of it that you've not used in games. One of the problems of revising is keeping things convenient that it's quick and easy to review when you need it. The other thing is managing what you need to review (things you forgot should be look at more than ones you remember). Again this is spaced repetition and other tricks to help here.
One system to do this is the flashcard system. It's described in the book 'Chess Master At Any Age' which has some neat ideas in it (although the flashcards are the best), but the main point is a symbol system (he trademarked it) that makes it easy to draw positions. Alternatively it's possible to get stamps of the pieces which correspondence players would have used, but symbols are way quicker.
Here is a link to an image showing the symbols: https://i.imgur.com/7HBqF5g.jpg
Note you don't have to use filled / unfilled, I use red pen and blue (felt-tip) pen which stands out over a printed board (you could also hand draw a board as in the image, but printing looks neater).
The cards themselves, should have a title, the position and who is to move, and some comment, possibly some analysis or the line (but too much and it defeats the purpose of a quick review). You can make them small to carry in a deck, but I prefer large and in a folder (although maybe I'll print some smaller ones for things I need to review often0. I used to use this as a method to review things long ago before I moved to a database (PGNs), but I feel databases aren't so useful for learning from and are hard to review and you need your computer..
I've attached a pdf of the paper I'm printing to make flashcards from the chessmood openings. It has a main board, and 3 smaller boards. I use the main board for the main position of the (sub) line and the 3 boards for further moves or analysis. This works well so far, but the real proof [of the pudding] will come when I start trying to revise from the format - so how good it is to help remember chessmood openings I am yet to see. However feel free to try it and see if it works for you.
Also you can use the same thing to take notes from the other courses for review later rather than having to find them again in the videos.
