I've always taken the direct approach also.
I simply ask them what they are waiting for? Can I get them something?.. Usually they go away then but if they respond with i'm waiting for xxx.
I tell them they might as well find something useful to do as it's still xx minutes away.
I've also found that putting them to work will clear them out in a hurry.
- "Hey can you grab me a water with a slice of lemon?" (hint don't drink it...)
- "Can you pass me a few napkins? It's hot as hell back here" (optionally - "and I need to light a Fire"
- "Got any spare towels the Chef stole all mine I'd really appreciate a spare"
- "Got spare change for a twenty I need to take the bus home"
- "Ask non-smokers for a pack of matches so you can light the stove, if they don't have any send em to the bar for some"
- " Ask smokers to go have one for you cause you're dying back here!"
If your pass has a view into the dining room - simply tell them to get out of the way, you can't see.
If they ask see what? - tell them if they don't see it they don't need to know.
With complete dunderheads I've been known to simply and politely tell them to go do their job and let me do mine. (gotta do it politely)
Back when I was a bit less mature... i'd simply throw something at them... messier the better. (not really recommended these days)
Singing a mildly innapropriate song or tune will clear them out of the pass also - but that would likely land you in a ton of trouble these days.
More on topic - laugh, lots and loud.
Take a deep breath and say something funny.
Break the tension and loose the tightness and then get back at it.
(i'd usually say something about another cook burning my steaks by turning the grill off or some nonsense)
(or that I thought the chef said 'burn em all day' or 'take the day off' etc)