[Skin Concerns] Dry scalp! Not dandruff, and tar/salicylic acid/zinc doesn't work.

My scalp is so, so dry. The rest of me is too, but I can easily take care of that. My scalp flakes whenever I move my hair, and it's kind of gross. I can barely wear black at this point. I also have a bad coping habit of picking at the plaques/patches the dryness forms, so I know I'm not helping it, but I can't get rid of the root problem (ha, root).
How do I moisturize my scalp? Can you exfoliate your scalp? I can't see a derm for a while due to insurance stuff, so DIY/drugstore stuff is really preferred.