I always open my valve partially to avoid a stuck sparge.... Not that I ever have , but just to set the grain bed.... I may be able to go faster if I tried.
I open it about a quarter of the way during vourlauf until it runs clear, then let it drain to the kettle at the same speed for a minute or two and then slowly and gently crank the ball-valve to full-open. Works like a charm and is pretty quick. Never had a stuck sparge on a normal mash... now, adding a few pounds of pumpkin is another story.