Those pliers look interesting, something from a James Bond movie?
I have tried several types of pullers, but couldn't get them down the plug hole far enough - those might do it though.

Over the years I have learned to warm the engine up a bit before pulling on the boots, this seems to help a lot. Same with removing stuck threads on the plugs, they seem to come out easier when warm.
Best way I found to pull on them is grab the metal part by hand and pull/push in a very straight line. The pushing-back motion seems to help loosen them up, sorta rocking them in-out.

But, get that dialectric grease on them next time.

Oh, you do know that the wires just unscrew from the boots, at least on the original wire sets. If you break a boot, and have an old spare, you can screw the new wire right into the old boot.

DG