I was just scanning forums and ran across your post. Ok, I have removed lots of freeze plugs which are not freeze plugs anyway. They are core plugs used to close the holes where the sand forms for the water jackets were supported. Trust me, I have personally seen two blocks cracked right through the middle of the core plugs. Anyway, back to your question. I just use a puch and hammer by tapping on the side of the plug. Once the plug makes an opening large enough to place a flat bit screwdriver in, just use it to push the plug toward the opening while continuing to tap. When the plug gets turned about a 45 degree angle, grip the plug with vise grips and pull it out. You can also take the puch and make a notch about 15 mm from the end to catch the edge of the plug. The 15mm that sticks past the plug will keep it from falling into the block as you use the punch to pry against the side of the hole. Be very careful not to hit the side of the cylinder bore because it can dent it.
I just removed 10 core plugs from an engine yesterday using only a punch and vise grips with no problems.
