What is a good cleansing for my scalp to get rid of build up?

i use a anti dandruff shampoo, its a recent choice, i usually stick to all natural stuff for my hair - my hair is completley natural and healthy so i was a bit reluctant to try it. but ive tried it now and i guess ill stick to it. now im worried about build up from the product. how long do you think i should wait inbetween cleanses, and how do i wash my hair of the chemicals (doesnt involve brushing it!!)