I was also struggling in verbal :)
I suggest you a few points, might help you
1) Get Aristotle SC grail, if you are non native speaker ( i am so, it worked out well along with manhattan SC )
2) For CR , Powerscore is good but very lenthy, rather i suggest you to prepare your own notes and your own strategy for each Q types and then practice it as much as possible
3) RC - go through the RC sessions of Ron - thursdays with ron, again carve out your own strategy, and then practice the strategy
Trust me this works :)
If you wanna know the sample strategy, drop me a mail i would share the same.
versatile801@gmail.com