How to get a set of 12 abdominals: crunches 2 sets, would it be possible to get significant mass in a few months?

Understand: The nature of the abdominal muscles(rectus, obliques and transversalis), for almost all peopel, aren't muscles which tend to "bulk" up. This is most commonly seen in those who utilize very heavy resistance training and steroids. Otherwise, don't expect to see very significant abdominal muscle hypertrophy. In fact, the key to a six pack isn't really the exercise but rather weight reduction!