There are many guides and tutorials for cleaning makeup brushes, some written/demonstrated by pros who are much more qualified than me to advise on the subject. But I keep getting asked how I wash and dry my brushes, and since I'm still working on my comprehensive brush guide (it takes forever), I figured this is a topic worth discussing.
I'm only semi-fussy about the soaps and detergents I use. Whatever shampoo I have on hand, Dr. Bronner soap, Caldrea gentle dish washing liquid-- they all work. I also use various face washes, especially Shu Uemura cleansing oil. I only have one rule: if it's bad for my skin it's also bad for the brushes. My hands are very sensitive and dry, so that's a good guideline as far as I'm concerned.
Another thing I do: condition. Natural hair brushes, just like or own hair, benefit from conditioning (synthetic brushes don't need it and can usually undergo a more vigorous washing with more stripping detergents, especially if you're suffering from acne and use liquid foundations and concealers). Again, I'm not fussy, and any conditioner formulated for dry hair will work (I'm partial to TreSemme for this purpose, as the bottle is massive and cheap). Do make sure to wash the conditioner thoroughly and then some, since product buildup reduces the brush's performance.
The most important thing in washing brushes, though, is to never ever soak the head above the ferrule. You need to make sure to let as little water as possible get into the base where the fibers are held together, otherwise the glue is softened and compromised and the brush will start disintegrating. So: as little soaking as possible and always in the shallowest water, even if it means placing ten different cups with varying levels of water on the counter.
Rinse in plenty of water, make sure the water run clean with no makeup or soap residue.
The rule of drying is always with the head down (again, to preserve the glue). That's why the cute brush tree from Benjabellle ($34.95, benjabelle.com) is a good solution. The design isn't perfect (I wish the silicone parts were stiffer as to not let the brushes move), but it's good and effective. I stick several brushes in each slot, except for massive kabuki brushes, and it keeps them in place with their head down and out of harm's way. The other essential drying aids are brush guards in various sizes (thebrushguard.com or through Amazon). They prevent splaying and loss of shape, and are the only way to make newer MAC 217 brushes last (it's infuriating how ten year old 217s retain their shape better than the newer ones, unless you use these hairnets). Yachiyo brushes (both Hakuhodo and NARS) also benefit from using these. Brush Guards come in four sizes and I use all of them. They make a visible difference and can restore even older brushes to a better state.
Now, as much work and thought as I put into washing the hair part of my brushes, I'm much harder on the handles. I make sure they're clean and shiny, often using wet wipes between washings, and I don't mind that some of them lose the embossed letters or numbers (Hakuhodo brushes are especially prone to it). Makeup brushes are tools, not home decor, so I want them clean and in tiptop shape, but don't mind normal wear and tear to their handles. That said, you can coat the handles in clear nail polish if that's your thing, and wash them gently.