I originally bought this for powder. However, since the bristles are synthetic, I thought I'd try how it works with creams and liquids - and it turns out to be a quick and effective way to apply my liquid foundation. It's soft, big and makes the whole process easier.
I use it in a sort of brisk sweeping motion, downwords and out (basically you don't want to go against the growth of that tiny peach fuzz most of us have on our face). Don't actually "paint" with the brush, just move it quickly and with a light hand as if you were dusting off powder. The coverage is more on the sheer side, as you would expect, but also very natural. I love how fast this technique is, it's basically a way of using foundation as tinted moisturiser on those days when you just need to even out your skintone, put on some mascara and be on your way.
And yes, it does work as an all-over powder brush too. :)