Maybe it isn't quite worthy of making a resolution, but the beginning of the year is a great time to think about how you clean and care for your makeup brushes. Start now with a good cleaning program, and with luck it will become a great new habit that will give your brushes a longer life span and boost the purity of the colors you apply.
The most common question about cleaning brushes is "how often?" That will depend a bit on what you're using them for and how many different shades you use. Most people use their foundation brush for only one shade, so that one is easiest, let's start there.
Foundation Brush - our #25 and #15 foundation brushes are made of taklon fiber, and when perfectly clean and dry, they are impossibly soft. As oils and foundation build up in the brush, it loses that wonderful pampering feel, so that is usually all the indication that I need that it's time to give the brush a good bath. Just an estimate, I probably wash my personal foundation brush every two to three weeks. I like to use a gentle bar soap for this one, so that the ferrule and handle stay as dry as possible, but you can also use a mild liquid soap in the palm of your hand. First, get the brush wet. Then either swirl the bristles on the bar soap or in the liquid soap in the palm of your hand. (Once you have gotten the bristles soapy on the bar soap, move to the palm of your hand.) Swirl the bristles until the foam coming out seems mostly clear. Then rinse. I usually hold the brush right in the stream from the faucet and rotate it, while combing through the bristles with my fingers. When the water seems to be running clear, squeeze the bristles gently in your hand. If a bit of white soap residue comes from the center of the brush, resume the rinsing. If foundation-colored residue comes out, return to the soap and repeat the sudsing. Because these two brushes have very dense bristles, it is common to need to soap up the bristles twice, or even three times. It is very important to get everything out of your brush. If you don't, it might feel (once it is dry) as if the center of the brush, near the base of the bristles has developed a hard area, and lost it's ability to be fluffy. This is just because residue is binding those center bristles together, and it needs to be rewashed and rinsed well. Once the bristles give up only clear water when squeezed, continue to squeeze until you can't get any more water out. Then squeeze them again with a towel over your hand. (If your brush is new, use an old one, the bristles can sometimes bleed a bit of black for the first few washings.) When you have squeezed as much as possible from the brushes, lay them to dry with the bristles extending over the edge of a countertop. My window-sill works perfectly for this! If you wash your brush immediately after you apply your foundation in the morning, it should be dry and ready to go the next morning. It is especially helpful if you fluff the bristles once or twice during the drying process.
Blush, Kitten and Buff Brushes - these three brushes are a bit easier to wash than the foundation brushes because the bristles are not as densely packed. The fluffier nature of them speeds up the lathering and rinsing process. I usually wash the three of them together, in nearly the same fashion as the foundation brushes...lather all three, then rinse all three, then squeeze and dry all three. If you change your blush color often, you might want to wash your blush brush more often, but you can also use an old hand-towel to do a quick intermediate cleanse between colors. To do this, either lightly dampen an area of the towel (a microfiber cloth also works nicely) and swirl the bristles on the damp area. Then swirl them on a dry area until the bristles feel dry. This will allow you to change colors without muddying the shades. If you use the same blush color most of the time, you can probably get away with cleaning your brush somewhere between every two and four weeks.
Eyeshadow Brushes - much like the Blush Brush, these brushes do well with a quick towel-cleanse if you change colors a lot. But because they also dry quickly, if you are making dramatic color changes, it is just as easy to wash them quickly after using a particularly vivid shade. To do a quick wash, I usually squirt a bit of handsoap in my palm and do a mini-version of the foundation brush cleanse. Because they dry so quickly, there should be no problem with them being ready to go the next morning. If you wear mostly the same types of shades, you can probably go two or three weeks between washes for shadow brushes. If you have more than two or three, I find it easiest to take a glass and pour a little liquid soap in, then add some warm water. (1 to 2" depth is plenty.) Take each brush and dip, swirl and pump until it seems clean. Put it aside, and when all brushes have been washed, rinse them one at a time, then squeeze to dry.
Eyeliner Brushes - in my bathroom, this brush is washed nearly every day. I generally apply my eyeliner with a damp brush, and if I don't clean it between, the bristles are hard and caked with color the next day--not an ideal way to start a beautiful liner look! Once I apply my eyeliner in the morning, I just rinse it off, swirl it on the bar of handsoap or in a touch of my facial cleanser in my palm. A quick rinse and pinch of the brushes between a towel, and it's pretty much ready to go again, even later the same day.
A word of caution on your brushes...never apply heat to them to speed the drying process. The taklon doesn't do well with heat, and using a hair-dryer will almost certainly ruin your brushes.