Either of the above tools is meant to be used to force out, swollen tipped glow plugs. The tips will swell from overheating and then they won't come out of the hole. Worst case, the tip breaks off inside the chamber, then you need to pull the fuel line an injector, to remove the broken tip.
Kip, simply clamping ViseGrips onto a swollen plug, and pulling and twisting can work, also. After buying the OTC tool, and trying to use it, my friend got frustrated and forced them out like that, instead. He is in Germany now, or I would borrow his tool and send it to you.