I was gifted a huge Purity several months ago. It's too harsh for my face, so I've been using it to wash brushes... Takes everything off.
I put the Purity in a shllow dish, wipe the wet brushes in and swirl them around. To finish, I hold them under warm, not hot, water to rinse being careful to only get the bristles wet. If the metal or wood area does keep getting wet, the bristles can come out.
They aren't really caked up or dirty when I wash them because I "clean" them with IT BRUSH LOVE spray each time I use them wiping them on a paper towel. It makes shampoo time much easier. It isn't necessary to clean blush, bronzer or brushes each time they're used, but I do spray clean my liquid foundation brushes and eye shadow brushes.
***Before the Purity arrived, I used Baby Shampoo. It worked just as well.