I purchased an Essence of Beauty concealer brush at CVS in a medium size. It's made of all synthetic fibers, and has the tapered "bristles" which picks up just the right amount of foundation which enables me to apply it directly where I need it. I also own several of their very small (eye makeup sized) concealer brushes which I use to apply my eye shadow. Same deal with that - the brushes are 100% synthetic, and grab just the right amount of shadow which makes apply it a breeze. Maybe you could try these brushes. They're inexpensive and really good.
CooCoo