I really recommend using the supplement throughout the year instead of just right before finals. Some of my classmates work off of old outlines from other students and literally type in what the professor adds into the outline, so that it's all right in front of them during class.
Not sure if this contributed to your problem, but i find studying in groups to be counterproductive. We spent so much time trying to arrange a meeting time/place/location that it just took away from actual studying. Now, i prefer to study alone and only consult a group to go over practice exams.
I agree. I too found study groups counterproductive, preferring to study and learn the law along the way, studying at the end with a few people to work out any kinks. Plus, it takes time to find out who you're compatible with and who to trust.