make sure you're doing a vigorous scalp massage (pads of fingers only- no scratching with fingernails) when cleansing. Don't just tickle your head,
If you're not massaging enough, I imagine that gunk can stay on your scalp. CO-washing really only works when the scalp is massaged really really well. It will take longer than just mushing regular ol' shampoo through your hair used to do, but it's so worth it. Your hair and scalp will feel so fresh and invigorated!