The first stage was to set up the character for the blend shapes by painting the weights into the face using the Edit Membership tool and the Paint Cluster Weights tool. I have never done this before and had to find video reference of how to use the Paint Cluster Weights tool but once I got the hang of it I was quite pleased with the results.
I used the Reduce and Smooth tools mostly to widen Melvin's mouth and make the skin smooth around it.
The next stage was to create a cluster for the mouth so that when it opens the cheeks also go inwards. This was done again using painting weights and then setting the cluster to be driven and the cheeks change shape as the jaw open joint is rotated on the axis.
The next stage and aim for the weekend is to create the blend shapes so that I can animate and test Melvin :)