Just finished the latest ghost head. For this one I built a form out of black cloth soaked in elmers glue and water, using a k-mart skull for the head and newspaper/packing tape for the bust. The great thing about this is that the result is pitch black in the black light, and even in the visible light it is almost impossible to see. Then I used the cloth stiffener and cheese cloth by dipping small pieces in the stiffener and then placing on the form. A small brush helps position the cheese cloth, and I tried to leave some cracks and voids, and allow the cheese cloth to role up some when placing it.
As you can see above, even in visible light you can barely make out the black cloth form.
It even looks decent in normal light.
In black light all of the irregularities really stand out.