Understanding OP's post more, I think this is kind of the wrong question to ask? Fluent speakers don't stutter period. Stuttering starts in the mind with anticipation and control. Fluent speakers may trip up over their words, but they never feel any sort of anticipation the way people who stutter do- hence you won't see stuff like facial contortions from them. I know you were just referring to visible dysfluencies here, but if you pay too much attention to that it seems you're missing mark that it all begins in the mind.