Shampoo buildup vs. Hairspray buildup?

There is buildup in my hair. I have a history of shampoo buildup (i think) and switch shampoos every once in a while. I was looking up remedies and I found one for 2 parts baking soda, 1 part water, but then I saw for hairspray buildup a mix of baking soda and shampoo. I use hairspray everyday now, to keep my hair straightened. But I dont know the difference between the two. My hair is kinda dry, but not too bad. But there's a real waxy buildup at my roots ESPECIALLY at the back where the part ends and brushes down, and then at my part too. So does anyone know whats up with my hair? Do these baking soda mixes work? Will they dry out my hair? Should I get a deep conditioner too/instead? Thank you for any advice.