I was the same way as you in undergrad, so in our first block of medical school I didn't know what to do. I tried a completely different method for studying that didn't work for me and ended up actually reverting back to my old undergrad method, with some changes.
In undergrad, I would make my own condensed note pack that was basically the PPT re-written and just write that out a few times and be golden for exams. But you're right, there's too much material in medical school to do it this way.
What I do now is make written notes for big concepts (flowcharts, tables, drawing of things, etc.) and put all the little details into flashcards (you can use Quizlit, Anki, Firecracker, whatever works for you. I currently use Quizlet, but I will be switching to Anki (zanki deck) in MS-II for board preparation reasons.) I usually have 1-2 pages of written notes and about 50 flashcards per hour of lecture.
By the time you have made your study materials (written notes + flashcards) you should have a solid conceptual understanding of the subject. You should put most of your time into the synthesis phase of study materials so that when you are making your 2nd (3rd, 4rth, etc.) pass, all you are doing is memorizing - you want to have the concepts already down. This is when you might read your textbook to figure out a concept or something. If you've made thorough study materials, you shouldn't theoretically have to look back at any powerpoints or read anymore out of your textbook.
When I adopted this method I began to do a lot better in school than I did in my first block. It works extremely well for conceptual topics (e.g. physiology), and is very time-consuming for topics like anatomy (because I like to make flashcards w/ unlabeled images. Now for anatomy I highlight everything I need to know in my Netter atlas, mark the pages with highlights, and just flip through that a few times a week. It's kinda like having flashcards except it doesn't take a lifetime to make them.)
Sorry if I was long-winded, I don't wanna study neuroanatomy so I'm just taking my sweet time with this.
Hope this helps! And remember: no matter how fool-proof you think your study method is, you will feel overwhelmed when you first get to medical school, and your study method will likely change in some way, shape, or form - even class to class (e.g. me with anatomy.) Just learn from your mistakes and do you best to be efficient with your time.
Ok! Back to studying. Good luck!