Ok, I had an idea based on what I *think* a plug spinner operates as. And since I have absolutely no experience with one I ask those of you who might know if this is even remotely close to what a plug spinner is.
Here goes, and I am sorry this is in paint but it is just a sketch.
http://pics.bbzzdd.com/users/Yossarian/plugspinner.jpg
Now the explanation behind this crude sketch. You take a pvc pipe, 1" I would imagine, and 2 endcaps with holes drilled in the middle of each large enough to fit a small metal rod through.
To make the plug spinner you would attach one end of the spring to one of the endcaps, and the other end to one side of the rod. The unattached end of the rod would go out through the the endcap with the spring attached. The pipe would cover the spring, and the other endcap would slid onto the rod keeping the portion of the rod witht he spring attached inside the pipe.
To keep the spring and rod easily able to move inside the pipe without sliding, center the rod in the pipe and solder a washer around the rod just outide of each endcap. Some other method, such as a gear and latch, or just a latch can be used to hold the rod once wound, I haven't made this but I would probably think something like this would work.
Last, flatten and temper each end as you would making a tension wrench.
Basically here is how it would work, you turn the pipe (in the direction to wind the spring, depends on which way you attached the spring) with the rod fixed, then hold it in place somehow (the latch), then put the plug spinner in and let the spring turn it for you. Of course the thing turns well only one direction so you have two ends that will move two different ways.