What I meant by studying systems as in FA is going through the appropriate anatomy, physiology, pharmacology and pathology while you're actually covering the system in class. For example, if you're doing your cardiology block: Go over the anatomy, physiology, pharmacology and pathology. This way, you're knocking out 4 subjects right there in one go. Yes, its very time consuming, but well worth it in my opinion. The sources are very dependent on you. I personally used FA for anatomy, BRS for physiology, Kaplan/FA for pharmacology and RR/ Lecture notes for pathology.
In addition to that, I also tried to knock out biochemistry or microbiology a little bit every week. For us, each block is about 3 weeks of material. The first two weeks, I would take out about 2 days each week, making it a total of 4 days (over 2 weeks) to finish up a whole subject, this left me with a week in the end to study for my block exams. This way, I had ample time each week to study my school material and stay on top of systems.
If you have a little bit of time to review, and you are unable to utilize a proper review book, pick up your FA and read it. At least you will have some idea on what you need to work on come intense board prep time.
I hope that makes a little more sense.