The simplest way to clean makeup brushes, including foundation, concealer, eyeliner, and eye shadow brushes, is to use baby shampoo. Simply wet the hairs of the brush in warm water then gently massage baby shampoo into the hairs. Depending on how long it’s been since your last brush cleaning, you may need to repeat a few more times. Once you are done cleaning, gently dry the brush with a paper towel. Then set the brush on a paper towel to dry. You may also need to reshape the hairs. Let dry completely before using.
How easy is that?
Essential Beauty Supplies has an easy step-by-step of this process as well.