Ive been fantasizing about an interrogation variation recently.  
  
Pretty much an interrogation with punishment.  
  
A simple example would be for the victim to hold an object or have a secret word. 
The interrogator would try to make him drop the object or say the word. 
  
Once achieved the interrogator would then subject the victim to a 1-2 minute punishment. 
Something severe enough to make him try extra hard not to give in next time around. 
  
After the punishment, the interrogation round is started again. 
  
*this could be really hot with two mistresses. One interrogator and one punisher. 
I can vision the punisher warning the victim not to give in while the interrogator is working him.