While using the Orb's crack brush try to vary the amount of pressure you apply. This added with basic knowledge of how cracks should look should net you good results.

Hello Zbrushers I'm a senior 3D environment artist working at blizzard, and It's been a while I didn't show new stuff so I decided to update my website and Art dump the work I did on the 'Heroes of The Storm' team on Zbrush central. Some of you may already know my work or a brush a shared a couple years ago called the 'Orb_cracks', this brush was created to make stylized stone cracks or wood lines, and I've seen a lot of people using it and sharing it. I decided to share my entire pack with the community, all the brushes I use everyday to achieve the style I want. Most of those brushes are behavior brushes so don't expect magic 'make art' brushes on all of them.

You can download the brush pack here, for free. Aankruwet: unfortunately I am not allowed to show wireframes, but they follow the highpoly decently. One thing that I keep in mind all the time when I sculpt is also the rule of 'edge definition', basically never going too sharp on my details, always 2,3 pixels thick minimum, so I never reach alliasing in game and you read details better from distance.

Also beveling, beveling as many shapes as possible, even cracks, every bevel is going to read better once baked, cuz it's gonna catch the light better. -- here's some breakdowns.