I would be scared to shave a balloon with a shave-ready straight. I can just see it popping and me dropping the blade in the ensuing nervous chaos and losing who knows what (fertility, a big toe, a shave-ready edge...) Thinking of this makes me think of the first Mighty Ducks movie where Goldberg, the goalie, is practicing to be a barber and he shaves a balloon

I agree that you are lucky to have a mentor.

Good luck and welcome,
Adam