First, take your skull that you want to make a cast of and cover in aluminum foil.
Next, using a 50/50 mix of white glue & water, brush the mix over the aluminum foil
Start adding layers of paper soaked in the glue/water mix over the skull, brushing over each layer. I brushed each layer with a dry brush, this helped to get the detail to show through. Put as many layers on as you wish, I did about 7/8 layers
Leave aside to dry. Once dry, take an Xacto knife and make a cut, the skull in half separating the back of the skull from the front.
Carefully remove the cast from the skull. It make take a little coaxing !
Join the two halves together by adding another 2/3 layers of paper mache. You can also tape the two halves together on the inside with masking or duct tape to hold the two halves together while covering the join.
Again set aside to dry, then paint and stain as required.
For my skull I first painted the entire skull in off white craft acrylic. Then line painted in the detail for the teeth with burnt umber craft acrylic. After this I brushed the skull with a dark minwax wood stain. After this dried I applied more stain to areas such as the eye sockets, jaw, temples, nose, brow etc.
Finally added more depth to the eye sockets and nose by painting with burnt umber acrylic and dry brushing other area for more definition.
I think the wrinkles on the skull add character to the skull
Total cost $0 (had already bought the skull I made a cast of, and the materials were already on hand)
The skull was cast last year, but was just recently painted. I intend to make a few more skulls this year and can take photos of the process if anyone is interested