I made a pair of these a while back and find them very usefull. Here is a simple graphic how to, I know this isn't rocket science but it might help some people.
Just a hemostat with small, medium, and large diameter gripping locations. The cylindrical grip areas help to not squash the insulation especially when hot from soldering. It also takes less pressure to hold the wire securely as it is captive in an approximately matching shape.
Small wire
Med wire
Large wire
Also acts as a very good third hand for contact pins by just laying it flat on the table. The smooth cylindrical gripping areas do not nick the gold plating and the pin cannot pivot like they always do in a alligator clip.
Start with your $3.00 Flea market curved hemostat. Look through all of them for the best ones. there is a wild variation of quality of grinding/shaping. Look for the best joint fit and general symmetry etc.
The grooves can be filed in with a small rat tail file. You can gently squeeze the hemostats closed and push the file through. Only stroke the section of the file that is the right diameter for the groove you are doing.
Small area done with the tip section of the file.
Medium area done with the middle of the file.
large area done with the back end of the file.
The method I prefer is to use a dremel tool with a Harbor freight diamond mandrel of the right size at 5000 rpm. The slow RPMS give you more time to react to what is going on and make corrections. I also axially stroke the mandrel to give a better finish. I gently close the hemostats on the rotating mandrel while keeping it in the right location and axially stroking back and forth at the same time. This keeps the two halves of the cylindrical grip area aligned with each other automatically. You may need to gently influence the mandrel one way or the other to keep the depth cut into each jaw equal.
Small
Med
Large
Use a needle file or diamond mandrel (shown) to deburr/radius all the edges so it won't nick wires or connector pins.
Use an abrasive bristle wheel to smooth/blend all the edges. Small dremel brush (slow cutting)
6" diameter brush on the lathe (awesome)
You may need to file the end to be flush with your first small diameter groove. Then you can file a nice rounded shape on the outside of the tip so you don't scratch or nick stuff when you are using this to cram a wire into an inaccessible area. The sanding sponge does a nice job of smoothing the file work and edges. These small finer grit ones are from the beauty shop supply stores (intended for fingernails)
You have just created a thing of beauty
You can bend the arms of the hemostat so that the gripping pressure is where you would like it on the first latching position. They typicaly have way too much pressure when latched for this purpose. So bend the arms so the pressure is just enough on the first latch position (not crushing the insulation). You can always go to the second latch position if you need more grip like when holding pins to solder them.