You build "brain power" by working on the speech mechanics. Ever since I started doing self-therapy, mostly in the form of practicing fluent speech techniques with an AI, my mental capacity for other activities has gone through the roof. My colleagues keep asking me where I get this energy from, and I tell them frankly that my whole life, I was getting mentally and physically drained by stuttering. Now, with daily practice, this iceberg of struggle (one where actual stuttering is just the tip of) has diminished to the point where I no longer need 2/3 of my brain just to awkwardly spit some words out in panic.