[Spirest]

Step 1.

Get the color that you are using as your base, then make a rough outline of what you are going to do.

Step 2.

Airbrush tool --> Smoothing 75%, Size 3, Opacity 190 <-- Choose a darker shade of color than what your base is, then airbrush where you think some shading or lowlights would go.

Step 3.

Airbrush tool --> Smoothing 75%, Size 3, Opacity 190 <-- Choose a lighter shade of the color, or white, and airbrush almost everywhere except near or where your shading has gone

Step 4.

Make a new layer, call it whatever, but make it Overlay and airbrush with a softer Opacity and wider brush over your highlights and closer to your shading.

You are now finished! Hope you enjoyed c: