^he's right, verbal can be quite different beast on each section, although ability to read quickly and clearly will help. i can only suggest doing mocks with only verbal, to see whether fatigue affects the clarity and focus. or perhaps going through idioms on MGMAT SC
guide. even native speakers would benefit from that gem of a chapter. other stuff, depends on whether you have native ear to guide you. even then knowing minute, subtle differences will help you answer marginally difficult questions just above your level. perhaps go through your notes, maybe reading something second time after few weeks will reinforce and strengthen your memory
remember that quite often most SC correction problems are wrong for more than one reason.
i don't know if this will help, use scratch paper to cross out stuff you know for sure is wrong, and also mark stuff that's probably wrong. use an x or something for definitely wrong, and one slash or something different for possibly wrong. will save you time from wasting time and also will focus your attention on where the answer is likely to be.