I can personally vouch for the e-gmat SC course. I took it and its pretty good to boost up your verbal score by a couple of points in a short time.
But I also think that it can only raise your score to a certain level. Above 36-37, you have to work yourself to distinguish stuffs and things should start to come naturally to you.
My suggestion is to spend A LOT of time with the official guide.
I personally think the wrong answers of each questions are wrong because of multiple reasons and the point blank rule is EVERYTHING that is used in the correct answer is ABSOLUTELY correct as far as the exam is concerned.
Sit with OG SC for a week. Remember that JUST SOLVING all the problems means NOTHING unless you are absolutely sure that you will not make the same mistake ever again. Analyze EVERY SINGLE OPTION of EVERY SINGLE PROBLEM. Look for modifiers, verb tense, meaning, parallelism to get a clear idea of how GMAT tricks you into marking a wrong answer choice. After you have mastered all the OG problems, I dont think there is a reason of not going 40+ on your verbal score.