I let my hair dread naturally. You only need to wash it once or twice a week. Twice at first, eventually only once ( if that often) whoever said every two days doesn't know much. ( I'm at nearly 9 years natural start) Brittle hair will probably knot well ( I assume you mean it's really dry from over washing) the point though of spacing out washing gradually is to stop your scalp over producing oils as a defence against washing too often. So first up that will help. Over time just add a day between washing, in a few months you should only feel the need to clean every 5 days at most as your head finds balance. I will let others suggest better shampoos as I use quite drying stuff like neutrogena T-gel, bicarbonate of soda, or even washing-up ( dish soap) liquid, and that's gone fuzz your brittle hair up even more. :/
mine are natural and i wash once a week. I second the above opinion that your hair will adapt to your wash schedule. My hair used to get really oily after three days but now it's totally fine with once a week, sometimes twice a week if I'm in a dirty environment like spraying chemicals everywhere, etc (I'm a cleaner). you don't have to take advice like gospel. By all means if washing too often is doing more harm then good, see what works good for your hair. Try and nice non residue shampoo and wash a little less often and see how your hair feels. Neutrogena sells a generic anti residue shampoo that I liked but I have bad dandruff so had to switch to t-gel.