Full disclosure: it's going to be an uphill battle. Improving verbal quickly isn't easy.
How many hours per day do you have to dedicate to studying? How much verbal studying have you done so far?
Is there a specific section of yours that is weaker than the others? What type of verbal score are you gunning to get?
My most immediate piece of advice for you (without knowing the answers to the questions above)
would be to just do as many verbal questions as you possibly can. All of the verbal sections require you to develop a certain degree of "feel" to perform well in them, which in my opinion can only be developed through practicing a LOT of questions. This is especially true of CR and RC sections, where the strategies you apply (find the purpose, summarize the paragraphs, constructing the syllogism, etc) are absolutely critical to answering correctly.
As for SC, if you've read the Manhattan textbook, I would think you have a solid "base" for SC theory. Again, just do as many SC questions as you possibly can.
I would work through the GMATClub "list of 150 hardest/easier SC questions". Start with the easy ones, then work your way up to the 700+s. And
be sure to review your answers to every single question you are unsure about, or got wrong. (Review questions using GMATClub posts - they typically provide a more intuitive explanation of answers than OG explanations do)