Washing my makeup brushes is one of my favorite things to do. I love it so much that I have been known to ask my friends if they need their brushes washed so I have more to do! (Yeah, I know I have issues)
I try to clean my brushes like once a week or so, but I also try to deep clean them every few weeks.
Here's how I do it:
First I run my brushes over a MAC Wipes to get off any excess makeup. With my liner brushes, I like to swirl them in a few drops of oil to completely dissolve the gel/liquid liner residue.
Then I mix a few squirts of shampoo in a cup filled halfway with warm water. I swirl each brush in the cup and then rinse gently to get rid of any suds and until all the makeup runs off.
I try and make sure that I hold the brushes upside down because if water gets into the barrel it can cause it to rust or loosen and come apart from the handle. And I try and wash my big brushes, like my Kabuki brushes and blush brushes, last because these tend to soak up the mix and take a bit longer to rinse clean.
Then I squeeze out the excess water and spritz each brush with surgical spirit to disinfect it.
And finally, I lay them down flat on a towel and make sure to shape the bristles so that they don't dry at a weird angle. They usually dry in a couple hours and then I have clean, soft fluffy brushes!