lots of custom brushes! Piles of them! I download a lot, make some, smash other ones together! I don't know how many of these are still in circulation in my library but the M@ sets and Goro sets over here www.pandemoniumart.net/brushes… are some of the first I started using, and I know I still use a bunch of them.
Those are also ollllld old brushsets, could probably find some newer ones from the same artists.
Obviously though you can get a ton done with just the default brushes. If I remember right Craig Mullins (who is an absolute beaaaaast) uses mostly default photoshop brushes (could be way wrong there... I think it was him, might have been someone else, dont quote me on that one)