This tutorial demonstrates a quick and simple way to create clothing in ZBrush by extruding a polygroup out from a Subtool.
Mask an area on the SubTool by holding down CTRL and painting on the Subtool.
In the Polygroups palette, click > Group Masked
Press CTRL + SHIFT and click the new polygroup to select it.
Under Geometry, make sure you have no subdivisions; the panel loop feature will not work on models with subdivisions. Remove subdivisions if it has them.
In the Geometry palette, expand the EdgeLoop section.
Click the Append button, which is just to the right of the Panel Loops button. This will create a back-face for your mesh so that you can separate it off and your mesh can have thickness without cutting a hole into the body underneath.
Increase thickness slightly with the Thickness slider. Try 0.02 for thickness, for example.
Click the Panel Loops button to see what you get.
CTRL + Z to undo an unwanted result and keep adjusting your thickness to what’s desired.
Now, if you turn on Polyframe mode, you’ll notice that the clothing item is its own new group with another polygroup at the edge(s).
If you want to get rid of the extra polygroup on the edge(s), you can go to Polygroups palette and click the Auto Groups button.
You can now CTRL + SHIFT + click on the new polygroup in order to isolate it.
Go to Subtools palette, expand the Split section, and click the Split Hidden button.
Now the item and the body from which you started are now two separate objects (two separate Subtools)