I totally sympathize, as I, too, experience itchy scalp. I've found the the co-wash I use is the biggest factor. I cannot use Suave (any of them) or Garnier Fructus Triple Nutrition. I can't use any of the cheap conditioners, period. Also, HESMU and TT give me a terrible case of the itchies. The more natural the product the better.
Luckily for me, I don't get flakes, just itch. I find using a scalp scrub brush helps a little. A really good rinse out of my cowash is a must.