Almost certainly originates from a TV coffee advert of the 70s/80s starring Gareth Hunt. He holds several coffee beans in a half-clenched fist then shakes them in a way reminiscent of a hand job. The relationship with Gareth Hunt is further strengthened since he was a considered to be a bit of a wanker.
She gave me a Nescafe Handshake
by pilonor January 17, 2009
Get the Nescafe Handshake mug.
British slang term to describe (in past tense) an insult by using the hand in a tossing/jacking off motion.

Nescafe (pronounced Nes-caf-a) is a coffee, who's ad on TV used a man (Gareth Hunt) that shook coffee beans in one hand like he was masterbating (very funny)
You are driving your car and someone cuts in front of you sharply. Lean out of the window, extend your arm and yell 'wanker!' while curling your hand and moving in a fast wanking/jacking off motion.

You have just performed 'The Nescafe Bean Shaker'!!

Ben "I was driving this morning and some prick cut me up!"
Bill "What did you do?"
Ben "I give it the old Nescafe bean shaker out the window"
Bill "No really?! ha ha"
by Clintos May 10, 2007
Get the Nescafe bean shaker mug.