i had this problem before xmas, i usually find that a pre-spray and then with brushing that in, the brush picks up all the hair, the problem i had was that the cat hair was so fine and lots of it that it wouldn't budge out of the pile, it was almost woven in. i made a 'broom' with a hack-saw blade on the end of a handle and it got some out but not really good enough but i would give that a try if all else fails, i think it would work on hair that isn't too fine.
colin