I agree with SheltieChe...
seriously, a dog will just get more and more and more frustrated with negative markers (plus it doesn't feel good for you, and it's not working...)
The dog will start anticipating and the behaviour may escalate.
Decide on what you DO want your dog to do during that time, because if you keep doing the same thing you will end up raising the intensity level of the negative marker to make it work and it is a vicious cycle.
Try and get the dog to associate what drives him crazy with something awesome so that he knows once this happens, rewards are dropping... do that before the arousal state is too high... I love the peanut butter idea, lol
It's a good idea to look into counter conditioning in my opinion...
here is a video of how Dr Sophia Yin does it
http://www.youtube.com/watch?v=sI13v9JgJu0:
OR if you don't have time for training it, keep the dog contained ;D
I have done this since Toffee is reactive to the toothbrush *sigh* I have broken it down to small steps.. I take toothbrush I drop treat... then get him out of bathroom so I brush my teeth in peace, lol... next time I pick up toothbrush, drop a treat put toothpaste on drop a treat, turn it on for half a second, drop a treat... etc etc.. if he barks at any of those times I go back one step to start again and then build higher and higher arousal scenarios each time as far as he can take it. It really made a difference... but does take time and patience. BUT what a difference and I never had to lay a hand on my dog nor get a frustration bite!
however I have 't had the patience yet to train this for vacuum or the blender, LOL . I just put him in another room if he is being completely loopy, lol... and that is managing a behaviour, lol
So don't feel bad it happens, just know that there are alternate methods of training and management of behaviours that will NOT make you grab a scruff or shake a dog or make you feel awful... Feel free to explore some of those and you will feel much less horrible because it empowers you AND the dog!!!!!