Confidence is useful, although I agree it can be limiting if you're doing the wrong things. I think the most bullet proof tool you can wield and develop is working on your mind. When you feel like you'll stutter, being able to release those stuttering thoughts. When you want to speak, focusing on your message and not how you'll convey something. In other words, don't reinforce the mental habits which are probably driving your stutter in the first place.