The next step for my Last Supper project was to add hair to the models.   I have very little experience with modeling/rendering hair in Blender, so this step was also more involved than I originally anticipated.  My intent was to create a rough draft of the hair, with another iteration of styling/coloring once the near-final lighting for the scene is complete.  So, from that point of view, I was successful,  but I still think the current result looks like a toupee factory exploded. :)

There is a good tutorial from CG Cookie that I used to get started.  

The learning curve for setting up hair particle systems was steep and I had the opportunity for multiple do-overs.  After the first success, though, each additional follification was fairly straightforward.   Here is a short list of the lessons learned:

• Separate the head/face into multiple zones (using vertex groups) to allow for slightly different styles of hair on each model.  Typically, I separated the face, the sides of the head and the top of the head, particularly if the hair was parted. 
• It is easier to shorten hair than to lengthen (within reason).   For my settings, the final hair length was a combination (multiplication) of the Overall Hair Length setting, the Children Length setting and the Kink Amplitude setting.   Two things complicate this; 1) the Overall Hair Length can't be edited once you start styling the hair, and 2) the Children Length setting can be set between 0 and 1.  This meant I usually set the Overall setting at a value larger than I thought I would need and lowered the Children setting to get hair the correct length.  Also, I set the Kink to Nothing until I had the shape of the hair roughed in.  Then I tweaked the amplitude and Children Length to get the correct length. 

• When styling hair, there is a difference between the Cut tool and the Length tool.  The Cut tool removed nodes from a hair strand.  Most of my hair used 6 points; cutting the hair reduced that number.  Using the length tool to shorten (or lengthen) the hair scaled the length without changing the number of points.  Once I figured that out, I rarely used the Cut tool.
• If, like me, you've been sleeping through the changes in the last several updates, you may not realize Blender now has a Hair Shader.  Some of the original learning curve was time spent in the material node creating a realistic looking hair material....until I noticed the Hair Shader.  Technically, the single Hair shader has two embedded shaders, Transmission and Reflection.  My results show I still need some tweaking, but they are a big time saver!
• Hair uses a fair amount of memory.  I created the hair particle system(s) for each model one at a time and was able to use GPU rendering to quickly render the affect of changing various settings.  However, memory requirements to render the entire scene meant I needed to switch to the CPU for the 'final' render.  I will probably turn the hair visibility off now until I am ready to complete another iteration of style and color tweaking.

Here is a render at the completion of this stage.  Creating materials for the clothes and the room/table are next on the list.  As always, comments are welcome.