Helping a tourist with STI problems

Last night we hosted a touring cyclist from Japan. He's ridden here from NYC and is on his way to LA, by a route that I think is too ambitious, given his time frame. He's a chef and was nice enough to cook dinner! He's riding a Jamis touring bike, disc brakes, Tiagra 2x10, very heavily loaded.
This morning he headed west about 10 AM, trying to beat oncoming rain. But at about 1 PM he sent me an email from 18 miles down the road, saying his bike stopped shifting. He'd tried but failed to fix it himself. Could I help? He thought he might have broken a rear shift cable, but wasn't sure.
I didn't get the email until later, but when I did I drove off into heavy traffic and rain to see if I could help. I took tools and spare cables. On the way, I encountered him backtracking, about five miles from my place - so having wasted about 30 miles. I loaded his bike onto my car's rack and drove him to my LBS.
The mechanic there is an old friend of mine. I was able to convince him to stop other work to fix the tourist's bike. Turns out that in fiddling, the young guy had completely unscrewed the adjustable cable stop on the rear derailleur. But fixing that still left complications.
This mechanic has long had the reputation of being the best in the area. (I've mentioned him before as the winner of the "fix a flat" race at a local cycling picnic event.) Still, he was quite frustrated by the front Tiagra STI lever. He seemed to be having trouble getting it set to the right condition to properly seat the cable end, then thread the cut end of the cable into the (totally enclosed) cable housing. It wasn't responding properly to the upshift or downshift levers.
Spraying the guts thoroughly with lubricant has been the only thing I've ever done to fix STI. Eventually, doing that enabled him to get the levers working again and allowed the repair to complete. As a result of all this, the young guy is going to do an extra overnight here.
To me, it's justification for my preference for bar end shifters for touring. I prefer simple devices with only visible problems.
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- Frank Krygowski