Can you try washing your scalp with minimal shampoo, just enough to get the dandruff out, and not letting much of the shampoo get on the ends of your hair? And/or get the bottom half of your hair oilier, could be with mayonnaise or conditioner, and tie it up in a loose knot before washing the scalp area. Then you can leave in some oil and clean up your scalp. I get dry ends but I like to have a clean scalp, so I do this sometimes.