A 20% gray Prismacolor marker was used for some slight shading instead of my beloved black Prismacolor artstix. I missed being able to shade subtle things like rosy cheeks, as well as major things like dark hair. However, I mentioned to all the parents that copies of these make great coloring-book-style projects for their kids to go to town on with their Crayolas. :-)
Here is a link to one of the masters of this particular style of live work, Mike Giblin in the UK. I checked out his stuff for inspiration before I did this gig.