Grounding on Lionel swithes

I am a little confused on the grounding of my Lionel switches.  I have 13 switches that are either Lionel 022 or Lionel 031 switches.  I am using one Z-1000 brick to power them and have a "hot" wire going from the brick to each switch.  I also have a control panel that uses the DZ1002 switch controls from Z-Stuff.  My question is in regard to the common wire.  If I run a common wire feed from the brick to one of the switches and then connect all of the grounds from the DZ1002's, will I be ok or do I need to run a common wire from each switch back to the DZ-1002?  Also, do I need to tie the common for the switches into the common that feeds my DCS signal.  I use both handles a Z-4000 to power my tracks.