Bad King has some great ZBrush tutorials and this one covers using masking and extracting to create a classic WWII Mk2 Fragmentation Grenade in ZBrush.

In this tutorial we create the classic WWII Mk2 Fragmentation Grenade where we utilise a number of techniques such as masking and extracting that have been covered in earlier tutorials. We look at Transpose lines and how they can be used to move and sculpt a model as well as introducing the clip brush. We also demonstrate how to shape a parametric model such a helix into a useable polymesh.

Part 2 of this tutorial will focus on making this model more realistic through the use of painting and detailing in ZBrush 4.