Loading the Brush with Soap:
Fill sink with hot water and soak brush for 3-5 minutes. This allows the bristles to retain and control the amount of water in the lather.
Follow all of the preceding directions for loading up your brush with soap.
Take the brush to your face and swirl/scrub/paint until the lather reaches a nice, thick consistency (peaks that stand).
Here's a great video that shows this technique, along with some others, for building lather: