A flaky scalp is a combination of an overgrowth of yeast on the scalp surface, and your immune system’s overreaction to that yeast overgrowth. If the body ignored this yeast overgrowth, because yeast is normally found on the surface of the skin, we wouldn't have a problem. If the yeast didn't grow rapidly on the surface of the skin, then we wouldn't have a problem either. So, targeting either of these two situations can really help control dandruff or seborrheic dermatitis.
Some of the basic over-the-counter therapies are a great place to start. Selsun Blue shampoo is a well-known one. Even Cortisone 10 can be very helpful, although it's a little tricky to get through thick hair onto the scalp. Your dermatologist may give you stronger topical steroids that are easier to place on the surface of the scalp. These can suppress flakiness and the immune system's overreaction to this pesky yeast.