Hi I came across your post, and I've HAD similar issues with my scalp. I used everything for dandruffs under the sun. Then I read about Bentonite Clay and ACV. It's now 2 months in and I have no flakes. This last time I co- wash instead of making a mud, I made like a codishpoo. This is what I used :
1 1/2 tsp clay
1/4 cup ACV
Any Conditioner on hand, fill 1/2 way
Water till you have 1/4 full
Rest with shampoo
Shake well
This is in a bottle that has a tip and you can squeeze out to hair/scalp. With that I was able to get 2 poo's out of it. But I co-wash with the Pantene Co-wash first.
This Bentonite clay is the best ever I've used to rid the dry flakey scalp. So hopes this helps