To work with zspheres as subtools:
- Press the Subtool > Append button for the model you are working with and select the zsphere tool from the popup.
- Switch to the new zsphere subtool. Switch on subtool transparency, so that you can see what you are doing.
- Using Scale and Move modes, resize and reposition the zsphere to suit.
- With subtool Transparency ON, model with zspheres as normal.
- With subtool Transparency OFF, click and drag to add zspheres that conform to the surface of the other subtools. Select a different start zsphere by clicking it while in Move mode.