Here are three tools that have been of use to me.
Weighted wrenches,
I made these years ago, to play around with the concept of having weights replace the pressure of your fingers. I didn't like the loss of feed back and control, so I seldom if ever use the weights anymore. They can come in handy to change picks, without losing set pins.
I do however like the way they fit the most popular keyways, nice taper for a snug fit, and good feedback, and for my hands the handles have a nice ergo feel
They are made of piano, or music wire. You can get this at hobby shops, and it's a great material for all kinds of projects.
The weights are fishing sinkers.
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8 in 1,
I'ts not a perfect fit, but there are some advantages in having eight sizes on one a twist flex wrench.
This was made from a wiper blade.
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Key blank wrench,
This seems to work best with the wrong keyblank. The proper blank fits a little loose because of the tolerance factor, It's pretty easy to find a key, that grabs the bottom ward tighter, and is wider for a secure keyway fit.(Some filing may be involved) This gives a firm feel in both directions, plenty of pick room, and no binding of plug to shell.
For years I used the wire through the hole, recently I lathe turned a handle that I really like. If you don't have a lathe, a small piece of all thread, with two jam nuts would do just fine, cover the handle with shrink tube.
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Buddy