I agree that abs should be worked like any other muscle. I've been doing this for 15+ years now, & what I've learned I've learned by doing it, not by reading about it.
When I first started I was told "if you want a 6 pack you have to shrink your abs, therefore you should overtrain them." So I did, like every day or every other day, hundreds of crunches, & nothing happened.
Then, sometime around 1996 or '97, I took a class on abs that basically debunked all the ab myths. They said "train your abs w/weights b/c to get a 6 pack you have to build the muscle, not shrink it" and that you shouldn't do abs more than twice a week, and you shouldn't do hundreds & hundreds of reps.
So I started doing cable crunches (4 sets of 15) and regular crunches w/a plate on top of my head (4 sets of 15) twice a week. The results have been truly amazing. And I have definitely gained that 6 pack.