You can add a bit of lemon juice to your conditioner too.
I knew I had build up when a couple of hair follicles became blocked and it caused a pimple in my scalp.
My sister, who relaxers her hair...knew she had build up when she would lower her head...and her long hair would not "fall" softly...but it stuck out as flat as a board. It was stiff and had no life. Once she clarified...it became soft and flowy again.