Fox and hound might work but you have to be careful as RF from one
wire might induce into wires next to it and you will end up with a
signal all over the place.

The fuse panel does come apart but I suspect putting it back together
would be quite a challenge it it's build the same way as the underhood
junction box. UHJB has a network of interconnections inside and I
wouldn't even touch it with a 10 foot pole....I might wrong though -
the fuse box might be built differently.

If you have sharp DVM probes, you might be able to pierce the
insulation of the wire and trace them that way.