Get some Johnson's Baby Shampoo (Walmart or any other store that carries such items) It's only about 98 cents. Use this every month or so to thoroughly clean your brushes. Mix some of the shampoo with warm water in a bowl then do one brush at a time and use your fingers to separate the bristles, but don't pull on them. If the water gets too murky then clean it and start again with your remaining brushes. This is sensitive enough on the bristles and won't irritate your face. Baby shampoo also works great as a makeup remover if you don't want to spend money on wipes or facial cleanser.
Then to keep your brushes clean in between the deep cleaning buy a spray bottle and some rubbing alcohol ($2 for both give or take a few cents). Combine one part rubbing alcohol with three parts water in the spray bottle and lay your brushes on a white towel or paper towel and spray the bristles well then rub them on the towel to get the excess makeup out and let air dry. The water will dilute the alcohol enough that it doesn't irritate your face, but will effectively clean your brushes.
So please before you go to some make up store and purchase a crazy expensive brush shampoo TRY THIS! It works I promise!