If you don't wash your makeup brushes, you are doing your skin a disservice.  Dirty makeup brushes can lead to breakouts!  I always clean my brushes once a week, it's simple and only takes a few seconds.  Every week I spray my brushes with Sephora Daily Brush Cleaner to the point where they are wet and lay them on a clean paper towel to dry.  I especially love this one because it's a spray bottle, so it's easy to use and it's antibacterial.  Since I don't wear heavy makeup on a daily basis, I really don't need to clean my brushes daily - weekly does the trick.
About every other week I use baby shampoo to thoroughly wash all my brushes.  I get warm soapy water and dip the brush head in the water and swirl it around.  After I finish that I allow the brushes to dry on a paper towel.  Simple and easy.  Don't want to wash your makeup brushes?  Use your fingers to apply your makeup! 

 
 
 
 
 
 
