When you say you are "done with the OG" does that mean you've done all the questions once through or that you've completed a detailed review of them? If you burned through them one time only, it might be worth your time to deconstruct them more deeply -- there's valuable information to be gleaned from mining all the different splits-- even the ones in the *wrong* answers, because they illustrate the way GMAT views the rules. Just burning through questions won't help you nearly as much as working through smaller chunks and then doing a really killer review. If you've mastered a question, you should be able to see it again and take it down really quickly--not because you remember the answer, but because you've deeply learned the grammar rules applied in that question, and have an efficient and repeatable process for eliminating answers that violate those rules.
Mixing that review in with new questions (the only other "official" source is the Verbal Supplement book) is a good way to cross-train for depth and speed.
Hope this helps.
JP Park | Manhattan GMAT Instructor | Los Angeles
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