when I drawing the eyeshadow or other makeups, I layout in PSD file with texture template on bottom layer.  Then set your working layer to 50-70% opacity so you can be coloring inside the lines. It sort of gives you a grid to work within.  If you don't have template or seam guide, check vendor or free stuff here.

The actual map may not have the unused areas delineated (because it is not necessary)