From the original article on how to remove a stuck valve cover (sorry - quoting isn't working for me...): "Get a long ratchet extension (I used a 3/8 drive 2 foot extension, ¼ drive may be more ideal as it is thinner) or similar sturdy rod and carefully slide it in between the VC and cylinder head. Place it firmly against the side of the spark plug tubes and with a hammer, give it a firm whack. Giving each spark plug tube a whack or two released them from the VC and made it possible for me to remove the valve cover leaving behind the spark plug tubes in the cylinder head."

I'm going to be doing VCGs soon, and am preparing for them to be stuck like everyone else's. I can't visualize where you had the ratchet extension going so that it is against a spark plug tube. Do you mean that it is between the valve cover and head, mostly parallel with the long axis of the head? Or did you stick it inside a spark plug tube where the spark plug is?