If I have to do some testing in an overhead electrical box with a multimeter, it is very hard to keep hands still enough to maintain the tips of probes on the wire because you are holding them overhead and your arms are shaking. Is there something (an extension for probes) or a technique with which multimeter probes can connect to wires coming out overhead?
Plug into most meters instead of regular probes.
If you have a small multimeter, you can stick it on your wrist with velcro, so you no longer need three hands. There are also probe-shaped multimeters that do the same thing.
But that won't solve your shaking hand problem.
Wire grippers are pretty nice. There's a long insulated shaft, and the pincers at the end are pretty versatile.
You'll need a pair of banana jack wires. Shrouded jacks eliminate the chance to zap yourself if the banana jack comes out of the hole and touches your hand, which is nice.
Once the wire grippers are in place, you also have a free hand to operate switches or do other things while looking at the multimeter, which is convenient.
Some multimeters have either min/max hold or automatic hold feature. These allow you to take the measurement without having to see the multimeter screen, and then check out the result afterwards. Thus you don't need to hold the probes still for very long.
With min/max hold, the meter records the largest and smallest value. You have to reset it manually before every measurement.
With automatic hold, the meter takes the value a fraction of second before it detects the probes as unconnected (0 or infinite reading, depending on measurement range).