There are brush cleaners that are made for quick cleanings such as Sephora Brand's Daily Brush Cleaner which you can find at: http://sephora.com/browse/product.jhtml?id=P208011
All you have to do is spray the brush cleaner on the brush and rub it against a Kleenex or papertowel until it wipes clean. Be sure to swipe the brushes back and forth and never jam them into the papertowel so the bristles retain their natural shape. Then lay flat on a clean towel to air dry.
However, once or twice a month I like to give my brushes a deep cleaning which I do with a mixture of baby shampoo and water. I just swirl my brushes in the mixture and keep pouring out the dirty water until the water is clean so I know that all the makeup and dirt has come out of the brushes and then I rinse and lay them flat on a towel to air dry. It's important that you always lay them flat to dry so that the bristles retain their shape.
I hope this helps you.