the general problem i had with CR and RC was timing. it took me ages to read the questions... so the first challenge was to pace myself.
at the end i was olving CR at about 2 mins/question or slightly less, spent about 3 mins reading each RC passage, and balance this long times by solving SC quite fast (about 1-1.25min/q).
once i found the timing the rest was less difficult. critical reaoning is after all critical reasoning... it is all about logic, not something which is language specific.
i never used "cracking methods" found in the prep books. jut thought about the matter logically.
however, the one concept that did help me from prep books was the concept of "scope". identifying scope of questions/pasages helped me rule out options quite fast, saving some reading. usually, after reading, and identifying the correct scope i left with only 2 options.
having said all that - find your own ways... critically try the methods offered in books, but listen to your mind and intuition to find what work for you best. some of the methods suggested in books (especially in math) or totally crap, but some can be the seed for your own peronal cracking method...
good luck.