I recently bought a pair of the new Rogue Element shock shaft pliers that were mentioned in the latest RC Car Action mag. They work as advertised, gripping the shaft without scratching while you thread ball ends on. I used to use a pair of Visegrips and a rag, which worked OK but not anywhere near as well as these purpose-built pliers.
I like them enough to make an unsolicited recommendation that they are a must-have tool in the RC tool box. Yes, they are pricey but they are very well made. You can find info and order from www.rogueelementcomponents.com
There's a pic below.