Second photo by the very talented Ming Wu
Step 1: What you'll need for the brain
To make the exposed brain you'll need:
-Brain shaped Jello mold (I got mine from http://www.thinkgeek.com)
Step 2: Make the brain
Mix a few drops of red paint into some liquid latex to give it a pink colour. Remember that the latex will dry much darker.
Pour a small layer of latex into the mold. Slowly build up layers of latex until you you have the desired thickness for the brain prosthetic.
Allow the latex to dry completely. This will take a very long time. Be patient.
Step 3: Trim to fit
Cut off the straggly edges and then trim the prosthetic until it fits comfortable on the side of your head.
Step 4: Apply the prosthetic
-Spirit gum (make sure you have spirit gum remover too for when you want to take it off)
-Make-up liquid latex
-Single ply toilet paper
-Red face paint
Shave your head so you have a nice clean surface to stick the brain on.
Coat the edges on the back of the brain with spirit gum. Position it on the side of your head and hold it in place while it dries.
Apply costume grade liquid latex around the edges of the brain. While the latex is still tacky, cover it with torn strips of toilet paper. This will disguise the edges of the brain. Cover the toilet paper with more latex and allow to dry.
Paint the latex and toilet paper with concealer so it looks like your skin. Carefully tear and peel back some of the edges to look like gashes. Paint the inside of the gashes with red face paint.
Finish getting ready to go out before adding generous amounts of fake blood.