such as the Extech or one sold by Blue Sea? These can be quite useful for finding breaker-blowing shorts. The problem with these faults is you have only a few milliseconds of test time before the circuit is open and no longer in its faulted state. The procedure with the clamp ammeter is: set it on "max" which records the maximum reading. Clamp it on the suspected circuit element. Activate the circuit, which will trip the breaker. If the fault lies in the branch of the circuit fed by the measured leg, you will see a high current "max" reading on the meter. Then work your way back (or forward) until you isolate. I have used this method a number of times and it is often a much faster and surer way of localizing the fault than using an ohmmeter. It is even possible to isolate to a hidden section of wire - current goes in this end but doesn't come out the other.

Good luck with it - these kinds of things can certainly try one's patience.