K.I.S.S.
Keep It Simple Stupid
Not trying to be offensive, but this principle applies here.
You can trouble shoot most of the wiring problems with a simple meter. Voltage, Resistance and Continuity will give you the indications to fix most of this. Whether the current is 10 amp or 30 amp in a circuit is irrelevant if that circuit is supposed to be dead / null at that point.
I suggest that you address the fuse you know to be going bad. Look it up on the wiring schematic and trace where it connects to per the schematic. Do a simple continuity check to those known points. If they check out all right, then the next step is to address those points that it definitely shouldn't have contact to. As soon as you find one of these, you have your first indication of where your short lies.
If you don't have the schematic, let me know whether your 260 is Automatic or Manual and I'll scan in the schematic and send it to you via e-mail.
Personally, I like the method Conor stated, pull the dash, and start checking the wiring harness for obvious melted wires. If that's totally unacceptable, then at least look at the obvious places that a wire could become loose / frayed or come in contact with stuff it shouldn't come in contact with.
Forget that multimeter, next someone is going to suggest you get a scope and a magnetic resonator and before long you'll be so deep into extraneous BS that you'll forget what you were originally going to do.
When you're up to your ass in alligators, all trying to bite you in the ass, it's really hard to keep in mind that the original reason for stepping into the water was to pull the plug to drain the swamp!