I hope you have seen this article on tatting with a needle used as if it were as shuttle:http://www.bellaonline.com/newsdtl.asp?name=tatting&date=7/31/2012%2012:05:39%20PM
It was followed by some comments from tatters:http://www.bellaonline.com/newsdtl.asp?name=tatting&date=8/1/2012%2011:40:30%20AM
And here is another good tip from Sue Draney Bundaberg Australia NATA #49:
"I have often used a needle to tatt in this method when I am at the end of a section and there is not enough thread to hold on the shuttle.
It is a way to finish a ring that is partly done when the shuttle runs out of thread."