I myself used to have horrible Seb Derb due to intestinal candidiasis from over prescribed anti-biotics.
What is working for is using an anti-fungal pro-biotic bar soap from "Candida Freedom". I have recommended this to many people suffering over the last few months.
It heals my Facial Seb Derm 100% and about 80% of my dandruff.
The bar soap itself is quite expensive (13$) but I plan to continue to use it until I fix my dysbiosis.
I know how miserable SB can be, hopefully it works as good for you as it did for me.