The exercise that helped me the most from speech therapy was talking to strangers (asking questions at a store) and trying to stutter on purpose. It's hard to make yourself do, but I was really able to feel the mechanics of it and feel in control. It's not a magic bullet and the effects "wear off" for me, but it's something I can repeat at work and get reinforced positive results. Practicing talking when you're alone helps too. Most of us can be pretty fluent when alone, so if I know I have some talking to do a certain day I'll just babble the whole way to work. Basically hosting an unrecorded posdcast. Even if fluency is effortless for you when you're alone (it is for me) still practice talking aloud just to get the muscle memory and confidence.