The engine service manual cautions (in strong terms) against allowing any remnant of the old gasket to get into the oil intake port in the block. Lest you clog an oil nozzle.

That's a pretty good trick in and of itself. I'll bet that it's technically impossible unless you've got a powerful vacuum nozzle following your every move with the scraper.

The "clean oil duct" is the dime-sized hole on the front, upper side of the mounting pad on the block. The service manual suggests covering or closing the bore. When I did mine, I found a cork that fit nicely. Then ensured the bore was clean after the scraping was complete.

That sounds like a perfect solution. Did you trust the cork to press it below the block face........to allow easy use of the scraper?

I just left the cork protruding and worked around it with the gasket scraper. The port is located such that it is no more than a slight inconvenience. Much less inconvenient than a blocked oil spray nozzle, I'm sure.