I hate to tune pianos, as many of the videos on my YouTube channel,
AeolianHall1, will attest to.  I use the Korg LCA 120 tuning machine,
which is about the size of a pack of cigarettes, and it is a miraculous
machine.  Google it.  For $70 or so, this is the best tuning machine
in my opinion.

I wanted to touch up the high treble on my piano, and since the Korg
tuning machine is so small I decided to put it down on the plate.
I realized that I could pluck individual strings with a toothpick.
Well, it worked so nicely that I was soon saying to myself that I will
never go back to the old style of tuning.  There's no need for muting
strips, rubber wedges, and all the other stuff -- all you need is the
Korg LCA 120, a tuning hammer, and a toothpick.  That's it!

Well, you also need to hold up the damper when tuning the trio of
strings that make up a note.  You can invent your own method of holding
up one damper at a time, which is easiest using a cushioned weight that
will hold the key down.

Does anyone know of others that use this method?

Randolph Herr