You don't need any fancy or expensive brush cleaner. You can use the same facial cleanser you use on your brushes. You can also use baby shampoo or antibacterial soap.
Squirt a little of the face wash or soap you're using into the palm of one hand. Wet the bristles of the brush and swirl them around in the soap so it lathers up. "Shampoo" your brush with the soap, and rinse. If your brush is extremely dirty or if you have been using creamy or liquid products with it, you may need to shampoo multiple times to get all of the makeup out of the bristles. Once your brush has been rinsed clean, gently squeeze all the excess water out and lay it flat on a towel to dry. You may want to rotate the brush every few hours to make sure all the sides get dry.
See how easy it is? Now a few tips...
Never wash your brushes in hot water. Lukewarm is fine. Hot water will melt the glue holding them together and make your brushes shed or fall apart.
Speaking of water, Whenever you're wetting your brushes, hold them bristle end pointing down under the water so you don't get water seeping into the ferrule and handle of your brush. You don't need to soak your makeup brushes. Ever. Your brushes were not designed to be sitting in water, and it's actually bad for them.
Some really fluffy brushes take a while to dry. Don't be tempted to blast them with a hair dryer - too hot! But you could always point a small fan their way to speed things along.
X's & O's and remember to keep it neat, FREAK!