mn, i've got some shadows that are solid black 
paint, and then i've got some that are... not 
sure quite how to explain it.  not precisely 
airbrishing (it's not paint, and has nice, sharp 
edges and a very even application), but similar 
to a light version of trace lines.  it's fairly 
fragile stuff; good thing it's usually sandwiched 
between layers of acetate!

lemme see if i can't dig up an example.

from LoGH.