So, I hung my bike up after a ride and noticed a thorn lodged in the front tubular. Pulled it out and pfffft .... well, at least I was lucky enough to make it home without flatting on the road.
The tire was already pre-treated with Tufo sealant per waytoomanybikes's
advice, and I added another half-tube (the small size tube) of sealant. It seems to have worked!
The puncture was on the side of the front tire - at the edge of the tread, almost on the sidewall - so I hung the bike by its rear wheel from a ceiling hook, added the sealant, inflated, and turned the front wheel at 90 degrees so it could spin parallel to the ground like a record on a turntable. That hopefully helped the sealant settle into the sidewall zone of the inner tube.
Before starting I actually masked the fork and downtube because I was worried about sealant spraying out. Didn't happen at all.
Quick, easy job except for the need to wipe up a few stray drips of sealant. Still waiting for the ultimate proof since I have not ridden on it yet since the fix. But the tire is inflated at full pressure and holding air.
If this holds, I am a Tufo sealant believer.