People ask me all the time which brushes to use for different things and now I can confidently answer that the Louise Young 34 brush is the best for foundation. I just got mine a couple of weeks ago and it makes applying my foundation a breeze. I especially love it in this summer heat because it makes the tiniest amount of foundation go a long way. I don't like wearing as much foundation when it's hot so I put a tiny dot on the tip of the brush and dab on each cheek, my forehead and my chin. Then I blend it in a circular motion from the inside and work my way out. This brush makes it so easy to apply a sheer amount of foundation! I'm in love!
If you're interested, you can order it here: http://m.nordstrom.com/s/3413313/