preferably one that is idiot proof. something I can throw in the fuse spot and run a wand over the crusty old wiring harness.

I know with a multimeter I could test everything individually, but i'm lacking time now days.

 

Interestingly, a multimeter will do just that. Throw one end on the fuse area and probe with the other end. Set the multimeter for continuity (i think) testing and it should beep when the wires are probes are connected.

 

^ Agree with farberio. The continuity tester on the multimeter will do just that. You will just need to place one probe in the fuse area and run the other to the end of cable that you are testing and that will tell you whether or not you have a short in the wire. I do not know of any other tool that can actually test for a short through the jacket as your suggesting with the wand though. I do have one that can do it with 110+ V, mainly for AC power, but the low voltage that runs through the car may be too low for something like that to work. Not sure.