I attended a MAC Pro class in Montreal several years ago. I now do this (after asking a lot of "how to" questions at the class, such as how to get bright colored pigment out of white brushes). I keep all of the brushes I've used during the week in a separate cup. At the end of the week I wash them. I line a cookie sheet (actually I use a jelly roll pan, helps to keep them on the pan), with paper towels. I put some brush cleaner into a glass bowl, I'm currently using Bobbi Brown. I dilute this brush cleaner with warm water. I put the most dirty brushes into the water and swish it around making a nice foamy solution. I have a second bowl of clear warm water and the faucet is running. I leave the most dirty brushes to soak while I start with my lightly used powder brushes (except those with stubborn pigment - more about those later). After I swish the lightly used powder brushes in the soapy foamy water, I swish the brushes in the clear water and then do a final rinse under the running water. After the brushes are rinsed, I run my fingers down the brush to lightly squeeze out all of the residual water and to lightly shape the brush, then lay them on the paper towel lined pan. After all of the powder brushes are done, I work on the more dirty brushes, those that I've used with foundation, concealer, eye liner gel, cream shadows, etc. I do the same thing, in the soapy water, into the clear water, under the running water, squeeze and lay on the pan.
All this time, I've left the pigment stained brushes in the cup. Now, this is the surprising thing I learned at the class. I asked the Professionals what to do to get the stains out of the white brushes and they said "use Dawn dish washing liquid". So I do, and yes, it works and my brushes are fine. I wet the brushes (there are usually about four or five each wee), hold the brushes in my hand and squirt a little Dawn soap directly onto the brush. I thoroughly work the soap through the bristles, then I thoroughly wash the soap out of the bristles in the bowl of clear water. Sometimes I have to refill the clear water several times to make sure all of the soap is out. I squeeze the brushes under the running water to make triple sure all of the soap is gone. Then I squeeze the excess water out of the brush and slightly shape and lay it on the pan.
I usually was about 25 brushes each week and this process takes about 15 minutes. If it's cold, the brushes take about 12 hours to dry. If it's warm, I'll put them outside on the patio and they dry in a few hours. Some of my brushes are more than 12 years old and look almost new. I don't lose bristles and have only had three, out of more than 60 brushes, have a problem with the wood on the handle flake off. The Dawn keeps my white brushes white, no blush or eye shadow pigment stains the brushes.
Hope this helps!
Then I use Dustyohunter's toilet paper drying trick and leave them overnight to dry. 
Thanks!
