I got lucky, the two books I recently wrote with Dara O'Kearney gave me a bird's eye view on how a professional thinks about ranges, so that helped me tremendously. If you browse poker forums a lot of people ask how to memorise ranges, it is a very common query and it is something I struggled with too. I think this means you can be more fluid in your play, it will help you in live poker and if a site bans any reference material you won't be at a disadvantage.
I defended (basic) charts recently but concluded that it is still probably better to study the ranges away from the table to internalise them, rather than have them on hand. There is a lot of talk about hand charts at the moment and whether a visual prompt is a crutch or even a form of cheating.
