Hi Clark,
I use those chisels a lot. Here is how I sharpen them. I use ceramic stones lubed with Balistol, water, and a little dish detergent mixed in a squeeze bottle. I also have a 5/8" diameter steel rod, which I polished and hardened. I hold the chisel like a pencil placing the face flat on the stone and hone it until well polished. Then I hold the rod on top of the stone right along the near edge, place the bottom of the chisel on top of the rod and the tip about 1/4" away from the far side of the stone. I slide it back and forth to hone the heel on the stone. The 5/8" rod keeps the chisel at the right angle to the stone to create the heel.
dave