How to remove dandruff from afro hair?

I’ve had cornrows now since last sunday, they are like freaking itchy, when I scratch, it’s all white stuff = dandruff. I once tried using head and shoulders, it works well and all that but once you stop using it you are in trouble! The dandruff that I had was much worse that the one before. I want to take out the cornrows and wash it with shampoo, the shampoo I use is smooth and sleek by Delon (In a big green bottle) and then just use some conditioner. What is I use garniers 2 in 1 shampoo and conditioner?
Is that better?
Also hwo should I maintain my hair? Sometimes I really have difficulties maintaing and styling it. Also how can I keep it soft? it’s really think.
If you want pictures you can check out my blog.
http://mylittlelonelycorner-estherni.blogspot.com/