Not only is it important to clean your makeup brushes for sanitary reasons but you should also do this on a regular basis because it helps keep them in their best shape to apply your makeup flawlessly. Once a month is fine as long as you are not experiencing breakouts.
I clean my larger face brushes first because they take the longest to dry. I use Bare Minerals, well-cared for brush conditioning shampoo, for these brushes because it gives them a good deep cleaning and keeps them fluffy and soft. If you are looking for a cheaper option baby shampoo will get the job done, but if you invested in high quality brushes I suggest also doing the same with the cleanser you choose. A little goes a long way so if you use it sparingly it should last you awhile. I apply a small amount to the brush and work up a lather. Be careful, it can come out fast! Then I run the brush under lukewarm water until the water runs clear. Repeat if necessary, then remove any excess water, reshape the brush and lie it on layered paper towels to dry.
Next, I clean my eye and lip brushes. I like to use MAC’s Brush Cleanser because not only does it clean them but also disinfects. For these smaller brushes I always use a small glass to pour the brush cleanser in and then I dip them in and gently swish them around (think of how you used to clean your paint brushes in art class). Then I run them under luke warm water and wipe them on a dry paper towel and then lay them to dry on the layered paper towels. A cheaper alternative to this is to use rubbing alcohol, but remember if you are trying to protect your investment this is just something to use in a pinch.
Then I just have to wait for them to dry! I usually will flip the brushes after one side is feeling dry, but it is not necessary. If I am in a complete rush I will use my blow dryer on low heat and power to speed up the process.
As I mentioned at the beginning of this post, once a month is normally all it takes to keep your brushes clean and extend their life. Any brush that comes in close contact with the inside of your eye, like an eyeliner brush, should be washed every time you use it. My favorite daily cleanser is Sephora’s Daily Makeup Brush Cleaner. It is an anti-bacterial formula that you spray on the brush, wipe it clean and let it air dry. I like to use this in-between my once a month deep cleanings to keep germs away. ( My professional brushes are cleaned in-between each client with this daily cleanser because it dries fast and then I deep clean them after I am finished with each job.)