Base on the diagnostic test that I took in the 12ed OG, my weakness was the Critical Reasoning, so that was the section that I began my studying on GMAT. I have finished the Princeton Review Crack GMAT, and MGMAT CR (up to the Strengthen the Conclusion chapter). I'm taking good notes as I go through the study guides. I have done all the questions (Assumption, Draw a Conclusion, and Strengthen the Conclusion) in the 2ed Verbal Review (without timing). At this point, I want to focus on how to get the correct answer before I work on speed. So far, I can only get about 50% of questions correct. In fact, I would spend 20+ minutes on some of the questions and I would still get it wrong. The GMAT CR questions seem to be more difficult compare to MGMAT CR questions. So, I need some help...

Here is how I approach a CR question:

1) Read the question first to determine how I approach the problem.
2) Read the argument.
3) Re-read the argument, but this time I would also do the "T-diagram" from MGMAT CR.
4) Read the answer choices and start eliminating wrong choice.

Usually, I can narrow it down to two choices, and that would probably expain my 50% accuracy. Nevertheless, I plan to finish the MGMAT CR.

1) Should I get the Powerscore CR to get a better understanding of GMAT CR? (How is PowerScore compare to MGMAT CR?) or should I start doing more problems in the 12ed OG?
2) Do I have a correct approach for doing CR problems?

Thanks in advance!