Could anyone give me any ideas on how to troubleshoot the following:

The left signal light on my 'Duke comes on and flashes at a regular pace for a few flashes before switching to double time - even though both front and rear lights continue to flash (so no burnt bulbs). After a few minutes the fuse ends up blowing. I took apart all the connections under the chin fairing to see if I got water in anything at the car wash but did not seem to find anything conclusive. There was a little oil left over from an oil change when I drained the tank and it ran down over the connectors (doh! - should not have used the shop stand), but nothing obvious was shorting.

Any idea where I should start?

You have the right bulbs in there 12V 21 W? obvious but maybe someone changed one during service or so?
No water in the indicators?
The other side is ok, no fuse that blows? If it's both sides could be the blinking relay.
take the lenses off and swap front left bulb with right, if the same try the back.
If the problem changes sides you found the issue.

Update:

After much frustration I ended up taking it to the shop where the also cleaned and tightened the connectors, and found nothing obvious. Somewhere along the line however the issue went away and after a couple of hours riding it there are no further issues. Because the motorcycle shop could not pin-point the issue they didn't even charge me! Really top shelf service and if you are ever in Calgary Alberta and require service the Old Motorcycle Shop is the place to go.

Cheers,

Bruce