I managed to grab a Tekno shock tool from my local Hobby People before they went out of business. Used it today on my new Coated shock rods, and I had already greased them up for installation and they pliers held solid. NO scratches or dings in the shafts. And there is a place that snaps the little balls in place and 17 and 12 MM section for tightening. Really a great tool, but I doubt I will use it more than a coule time a year. But I guess that's why we buy tools. That way the next time we need it, we don't have to buy it.
I haven't tried them yet but I believe the ball joint pliers from my helicopter days would work.
They have a little cut out on them that is used for holding the shafts for tightening the ball joints.
They also hold the feathering shaft to help get it out of the head. https://hobbyking.com/en_us/curved-ball-link-pliers-5mm-1.html
here is a sample of what I am talking about.
As already stated, the correct tool for this is a shock shaft plier with the correct diameter for your shafts. The Tekno tool is 3 and 4mm but doesn't have 3.5mm. The alternatives all end up working when they effectively avoid scoring the shafts which is the point of not using bare visegrips