That sounds like quite the typical case: Kids in speech therapy don't typically get to the more advanced stuff, and the therapists they encounter don't typically do much with them beyond simple, or perhaps even misleading, stuff. "Slowing down" is not a technique. It's just a standard phrase that gets thrown around. You should go find some proper speech therapy now that you're older. Maybe it'll help you feel more at ease with regards to working in a communications job. Not to say you can't work in such a place if you stutter, mind you. I stutter frequently, but the people I work with don't mind. Strangers don't mind either. It's just a thing, innit.