I do not like the brush that comes with it and bought a cheap small eyeliner brush that I use. I use the waterproof formula and am not sure if the first one is the waterproof one, but at least you'll know what to look for.
E.L.F. at Target or online has a waterproof pen type eyeliner for $1! I've used it for a few years now. Almost all of their make-up is $1 all the time.