Your prep materials appear sufficient to tackle your goal.
I had the same problem with verbal (SC). I did the following after completing the Manhattan GMAT SC
1. Using the Official Verbal Guide (GMAC), I split the SC questions into blocks of 10, and went through as many blocks in a given day as time would allow (budgeting the 2 min/question).
2. When guessing on a problem, I would mark that problem.
3. When grading the completed blocks for the day, I would mark the ones I got wrong (different marking from the guessing). I would NOT mark the correct answer.
4. After completing the entire set, I didn't study SC the following day. The day after, I would go through the ones I missed and the ones I guessed on (using a new sheet of paper).
5. After completing those in one sitting, I would then review and figure out why my approach was wrong.
I felt this method helped me a LOT. I could not break 700 for the life of me, due to verbal (most notably SC). I was scoring in the upper 40s in quant, no issues there.
After figuring out why my approach was wrong on the more difficult SC questions, I was in a better position to score higher the verbal section overall. I found certain strategies for SC (split/re-split) could not be used on all questions, thus I had to have more than one approach to the problem.
Note: I REALLY had to learn the material to effectively apply the strategies. Other GMAT prep books/programs might tell you to "listen and answer with your ear". If you're like me and think the same way you speak, that approach will lead you to wrong answers more often than right answers. Focusing on the material (tense, pronouns, agreement in #, etc.) is key.
Hopefully this helps.
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