One of the things Keith recommends in A Twist of the Wrist is to have a track map and as you identify reference points, come in and mark them on the map and write down a description of the each mark, what it looks like and how you are using it. That might help you remember them, since it it not only reminds you right away after your ride session, it also 'records' the references in your brain in a different way (by describing each one with words) versus just relying on remembering them visually as a picture. And, of course, it gives you a record to go back and look at the next time you ride that track, reviewing your prior RP notes can REALLY help get you located on the track more quickly the next time.
It also may help to prioritize the references you need and want, so you can go out each ride session and nail down just a few at a time (per session) rather than trying to identify and retain a lot of them all at once. For example, decide that you need to choose a specific apex in Turn 3, and a visual reference so you know where to crest the hill in the blind area in Turn 9, and just go find those two references in a ride session, and write them down. Then in your next session pick up a few more, etc. Trying to get 3 or more reference points in every corner in the first session or two of a day can be overwhelming and cause them all to sort of run together or get muddled in your head.
As far as picking them up more quickly, using the 3 step technique (do you remember that?) and/or Wide View can help you see the shape of the corners and open up your vision which helps with finding RPs.