Have been trying to think of a way to make this DIY project a bit less "DIY" looking, although I'm all about pulling a DIY object out to show someone and they are completely befuddled as to what it is and what it's used for hehe.
Best way I can think to do it I tried to put down in an image. It's pretty rough, but I'll try to explain.
Ok. Yeah, rough. I know.
Ok, a quick description of what's what:
A - Forend Piece
B - Tailend Piece. Flared out at the end for gripability (yay for new words)
C - Plunger
D - Straight piece of metal in place of a tention wrench
Oh, and the general idea here is the entire aparatus is round, save the flat piece of metal (D) to be directly inserted into the plug.
Ok, here it goes:
Piece A and D would be solid and would rotate together, but piece D would rotate freely inside piece C. Piece A would have two male notches extending towards the tail end (shown in the EXTERNAL angle) so as to grab onto piece B, which would have the appropriate matching female recepticles. The male / female pairings would be, looking at like a clock, at a 12 / 6 orientation. This would allow the spring to be wound 180 degrees either direction.
Piece C would be a generally round piece, save the two pieces extending on either side. This would be done to prevent piece C from rotating inside piece B to create torque. It would slide in and out within piece B.
The spring it's self (which I could not find a decent way to depict this) would be stradled between piece A and C, using the wirey ends to anchor the spring into either piece.
Once it'd be assembled, you would pull piece A towards the forend of the tool to seperate it from piece B, allowing it to be turned freely. You would then twist piece A 180 degrees one way or another to suit the situation, and then slide it rearwards back onto piece B's female recepticles, holding piece A in a tentioned state. This would allow you to get the spinner from the "torque loading" state to the end of the lock. Once inserted thusly, you would simply grasp piece B between two fingers (I invision myself using it between my middle and ring finger), and then use your thumb to press piece C into piece B. This would free piece A, the torque would release, and the plug would spin.
Crafting-wise, I'd think using a combination of a mill and a lathe would produce the best results. The particulars of the spring I haven't worked out yet. Such as how you would secure it to both piece A and C.
plug spinning? looks cool tho! 
