There are cable clamp signal generators made specifically for this- you clamp them at one end and walk along with a trace probe which can track them through walls. We use them all the time for tracking data cables; I've never personally used one for power cables, but I've seen them, our one meter had clamp attachments for it and probes for finding leakage from broken underground cables too. There is some issue with bleed-over to other nearby circuits when it branches out, but the signal is always attenuated on the other cables, and strongest on the one you're tracking.
If you know where the cable end points are, your solution sounds easiest. In fact, I did the exact same thing last week- used a small microwave (manually) pulsed on and off to verify which circuit breaker was feeding the string. A 10A pulse is hard to mistake!
[This message has been edited by SteveFehr (edited 09-28-2006).]
