It's a good idea to disconnect the fuel source and run the engine until it's out of any remaining fuel. I use one of these to ground the plug wires.
http://www.ebay.com/itm/350939409893
I've seen someone leave all 6 plugs dangling out while fuel mist sprayed out of the 5 cylinders. Let's just say I'm glad there was a fire extinguisher close by.