One of my favorite sharpening tools is a diamond paddle.
I use it for router bits, knives and, most importantly, scrapers.
The problem is that it cuts so fast the tiny spaces between
the diamonds quickly fill with metal particles, called swarf,
which slows or even stops the cutting action. Most instructions
suggest using water to wash away the swarf. Water
works well enough, but household oil works much faster.
Every sharpening tool, whether it’s a file, waterstone,
sandpaper or this diamond paddle, cuts faster when it’s free
of swarf buildup. Fast is good, because the fewer strokes you
take, the more accurate you’ll be.