England's King George VI seemed to benefit from breath control.

Writer-photographer, Lewis Carroll was adept at word substitution and cultivated a slow and deliberate style of speech which eventually led to his being able to preach to a congregation with some confidence.

The writer, John Updike, tries to avoid speaking engagements where he is forced to read material he hasn't written.
John Updike on NBC, 2/96

British Prime Minister Winston Churchill got his vocal cords vibrating as a warm-up before speaking and found it helpful to know exactly what he was going to say in advance.
Winston Churchill, 5/45

Actress Marilyn Monroe learned to speak with a breathy, hushed voice to avoid stuttering.
Marilyn Monroe

Singing their words proved successful for singers Carly Simon and Mel Tillis, who sometimes stuttered in speech but not when singing.
Carly Simon on NBC, 12/95
Mel Tillis on NBC, 12/84

Actor James Earl Jones finds reading aloud from a script effective.
James Earl Jones on NBC, 9/93

The writer, Henry James, constantly used interjections like "well," "er," "um," to complete a sound.

Biblical phrases refer to stuttering in Moses, who begged his god, Yahweh, to release him from the task of delivering the Hebrews from Egypt for fear his voice would fail him (Exodus 4:1,10): … " They will not believe me, nor hearken unto my voice…: but I am slow of speech and of a slow tongue."