The best thing that I have ever found is baking soda. Apply it to your hair coating every strand. Rinse it out with warm water. Then shampoo and condition as normal. The buildup will be gone.
I use to clean my hair by henna twice a month. Henna and Amla herbal hair oil is natural hair protector which makes hair clean. They protect from the root itself. They also help to control dandruff, loosing hair. Natural hair protection is better than the usage of chemicals
If your hair has old, built up soils in it, a good old-fashioned way to remove the build up it to first wash your hair as you regularly would. Rinse your hair well then pour white vinegar into the hair, scrub and rinse out.
I stumbled upon a solution when I realized I was out of shampoo and needed to wash my hair. I tried dish washing liquid and I noticed that my hair felt cleaner than ever. I use it once a month to remove build up.
Daily Clarifying Shampoo by Neutrogena is one of the easiest ways to reduce the dulling effects due to build up of creme rinses, hair gels and hairspray. If the build up is causing excessive dullness, a hot oil treatment may be necessary.