You need to time your reviews (I would do an hour per lecture). If you are trying to memorize every detail, you are doing it wrong. Once you are done you have to go back see what your are retaining and understanding. If there are things that slow you down, you have another session mainly focusing on these tougher topics.
Also there are things professors love to teach, and this is the stuff tested on exams and are usually board relevant. Highlight things that the professor mentions in class and go over that first and foremost before going more into depth with other material. This will drastically cut down the material you will need to retain.
When you are in your study groups, your study buddies who are awesome at retention will help you with the details that fill the holes in conceptual knowledge. They will also tell you what they think is high yield. It is insane how many time my friends saved me on exams.
As for pounding questions, this is what I do after a couple reviews (i.e. 1st review will be w/ power points, 2nd might be with other sources if I didn't understand slides) to make sure I truly understand the material. It help because it gets you into the test mentality and also helps to see where the holes in knowledge are.
The key really is going superficial first and then deep, don't worry if you don't understand it all on the first pass. Jolt down what you think you have a hard time with and save it for the second pass. Make sure to use any outside resource: youtube, BRS, etc. for your second pass with the though stuff. The third could be with your study buddies and/or doing questions. This has helped a great deal.
If you have any questions, let me know.
