it appears bill may have attached "Cellular node in Mode 3 with Turbulence=2" and diffuse node to colour math subtract node, then attached colour math subtract node to fresnel blend inner channel.   in response to hana's post below, bill's candy paint shader does have around 50 - 100 nodes, but this might be the basic method.  I recall using the candy paint shader, hence it may have been a freebie already.