Hi All,
If memory serves me correctly,
On the A320 family with the CFM engines you must intervene in the event of a "Overspeed Protection Fault" or a loss of AC power (ie APU failure during first engine start).
So, hand on the Master switch, but no other intervention required.
On the A340/A330 fleet with CFMs or Trents, no intervention required at all, so hands off the Master Switch.
regards,
Bruce Waddington