A different situation, I know, but my parents were advised (by a trainer) to use a water spray to discourage their then pup's barking at other dogs and it led to a serious dog aggression problem that took years to get to a manageable level.... she still barely tolerates other dogs and has never, even as a pup, played with another dog.
I don't see what is wrong with a pup being in a pen when unsupervised - you still have the opportunity to redirect chewing of inappropriate stuff onto appropriate stuff when you are there, and this way you are teaching a pup what it IS allowed to chew.... rather than, perhaps, just making it scared to chew something in front of you (but it may well still be safe to chew things when you're not around, as the water spray doesn't happen then...).
Again, a different situation, but I saw on an "It's me or the Dog" special this weekend a noise aversion technique in use to stop a dog raiding a bin.... they set this up so they could sound the alarm remotely, so that when she tried to raid the bin, even without someone there, they could sound the alarm. It worked at first.... but they hadn't dealt with any other issue (maybe lack of mental stimulation, a more interesting/challenging way of obtaining food, I don't know) so after a few weeks she figured out how to open the fridge and raided that instead...