I am absolutely still in love with my CND proseries. I have the #10, and it may be big, but I've been using it for everything. The bristles always go back to a point so it's perfect for little beads. It can flatten into a great shape for infills or full sets. It's just such a sexy brush!
For starters, you may want to start off with a #8 brush. It's not too big, but not too small. And you have to take really good care of them. If you're not careful, you'll get hardened acrylic stuck in the bristles, making the brush trashed. Clean it after you're done using it ASAP- reshape the bristles and put a cap over it to protect the brush head, and try not to pick up beads or "stab" your beads onto the nail in a way where product will get stuck inbetween the hairs of your brush. x