I am listening to a show on the radio here with a behaviourist on the show.
she made mention to a bullog in particular to how
sensitive the bully is to noise and people that raise their voices..
instead of using the word NO..
clang two pans together instead.
you will get a far better response out of the bully..and also.......
it is far less stress on the dog

personally I suggest learning the sign for NO..lol. but that does not always work. with Gus being deaf the pans would not help...