Hello, Krafty
Hankens are done all by hand and not xeroxed on the front like 99% of all other production cels.
Normal Production cels are done by taking the production drawing and xeroxing the drawing on the front of the cel and hand painting on the back to fill in the colors.
Hankens are drawn free hand some with pen some with a paint brush for the lines on the front and hand painted on the back for the color and are done on a large cel so when it is sized down it shows more detail on the end product and on some so it can wrap around the whole DVD/Video box.
The drawing is done by the head animator at the production houses most of the time and only a few are ever done for each show and this fact is what makes them cost so much.
The same Inks,Paints ect are used to do the hankens but more time is spent on the art to make it look it's best for the ads or covers.
If you look at alot of covers they look a whole lot better than the art in the show.
here is a few to look at.
http://backlotanimation.rubberslug.com/gallery/master_query.asp?SeriesID=17082
I hope this info helps a little.
Roy