I'm thinking of doing this myself. With the power off, batteries disconnected, you'd clip the tone generator to the Power port's (cig lighter) power lead and ground. Then go to the fuse blocks, touching each fuse, and listening for the loudest tone from the probe. The problem I've had before is the signal "bleeding" to other circuits at the panel. I've not tried it on the MH yet.
There are several devices out there, this had good reviews:
The Fred and Barney way is to make a continuity test. Get a low voltage buzzer tied to 9v battery and add clips to either end. That's clipped to the power lead of the cig lighter and ground. Next, open a paper clip into a narrow "U" like a bobby pin, then pull the fuses insert it into each socket. Take a photo on your phone before pulling the fuses or one at a time.