skeleton costume here is an attempt at making an accurate skull with face paint to line up with the hat. This was the best photo i had but it was before a little bit of detail was added.
I used the Rainbow Face Painting Kit from amazon. Pretty happy with the kit. You might want to have a few more brushes then the one it comes with. I mostly used a 1/2" brush to do the large spaces. Then used a fine brush to make the sutures and blended them into the white.
The tips I have are:
The best way to go is to take a look at a real skull image while painting.
Start with the white and add the black after.
Feel the cheekbone, jaw and eyes to correctly make the shapes.