First, create a small belt with three Polygroups. The first Polygroup is the end of the belt, the second Polygroup is the middle section of the belt (this is repeated along the stroke) and the third is the belt buckle. Make sure that all three polygroups are the same relative height. With the belt facing the camera plane, click the CreateInsertMultiMesh button in the Brush palette, then activate CurveMode in the Stroke palette.
To add variation to the belt duplicate the original 7 times and change the middle section for every duplicate. In Brush>Modifiers turn on Weld Points, turn up Curv Res, Variations to 8 and Variations Selector to 3 for randomness in the middle Polygroup when the brush is drawn out. To make sure all the pieces weld, each piece has the appropriate opening and the vertex points match at the ends of each Polygroup.
Now we’ll complete the belt. When the curve is drawn out we will need to break the rule of making sure that all three Polygroups are around the same height. If you make the first and second Polygroup larger then the belt will be completely closed off when drawn out.
If you want the curve to completely wrap around a surface make sure to hold the Shift key and keep moving your brush outside of the mesh. You will see that ZBrush creates a complete curve around your mesh.