I reckon from my recent experiences the best thing to do after readding the
MGMAT books is to do lots of questions, like RKimball said (the very helpful
MGMAT instructor), and when you get a question wrong, either completely master it by understanding the
MGMAT OG Guide answer and the OG guide's answer, work out which was the best one to use, and then mark the question to be done again very soon, to cement the knowledge in your memory. And if you get a question wrong due to lack of knowledge of a concept, do 5-6 similar questions, then mark the question to be redone again very soon. Also apply this concept to GMAT Club practice exams and other practice CATS you do. Make a list of those particular problems and concept areas you are weak in so you can focus on nailing them.
I'm doing this now and I can tell you even in 1 week my retention of knowledge has accelerated massively. I've wasted so many months on this damned exam purely due to not studying properly or effectively, now I see the light at the end of the tunnel!