Have you tried Giovanni Tea Tree Triple Treat Shampoo? It's a low-poo, and it really helps with itchy scalp and smells wonderful! This time of year my scalp can get really itchy!
Also, are you massaging your scalp enough when you co-wash? In the beginning, I wasn't doing it enough. Now I do, and I rarely have flakes, which amazes me!
Every once in awhile (usually every few months), I have to use a sulfate shampoo on my scalp. If it feels gunky and itchy, then that's what I do. Sometimes we just need that total clarifying that a sulfate shampoo gives. I go as long as I can without using it.
-3a/3b, fine, very thick, normal por., normal elast., long, dye- free (CG since Nov. '11)
-CO: every other night (air dry) VO5 (various scents), As I Am Coconut Co-Wash
-Low poo (As needed): ION Color Defense Clarifying, Yes To line, Giovanni TTTT
-RO: GVP CB, VO5 Split Ends, Herbal Essence Totally Twisted
-LI: Giovanni DLI or a tiny bit of my co-wash or RO (sometimes none)
-Styling: BYZ Noodle Head Tame your Curls Mousse or Jessicurl Spiralicious
-PT: ION Effective Care