blitz
...I am assuming you mean which sections I had problems in the verbal section... Yes, that is what I meant.
I am sure you have gone thru
MGMAT SC guide atleast once already. The rules in SC are aplenty but finite, so given enough time, there is no reason why you can not master them all. If time is a constraint, you may want to focus only on the rules asked most frequently.
Unfortunately, there is no shortcut for RC. You will have to read the full passage atleast once (maybe more) and thats that. Lots of book would suggest you to just skim the passage once and then keep coming back to it to answer the questions. I have found that mehtod more time consuming than actively reading the passage first time around. Additionally, you may also want to do some 5-10 LSAT RC passages. That material is generally tougher than GMAT and thus raises your comprehension and speed.
Ofcourse, what works for me may not work for you. Taking GMAT again is not a bad idea (I personally improved from 660 to 760) but lets leave that for a later time.