Just about anything works if you go into it seriously wanting to make change. Just a change in mindset can have a significant impact on your fluency. If you went to speech therapy you should have some strategies at your disposal, but I never really liked to use them and still don’t most of the time, you might be the same way. Breathing exercises work for me just because they keep me calm, which in turn makes me stutter less. The more comfortable you are with your stutter the less you’ll do it because you won’t have that fear of messing up.