You will need to create a mask to protect the for the skin. Add a bit of red with the Color Spray, a and then adjust the Alpha RGB and paint over the the lower face to indicate. We just want to break up the surface a little, so let's use the Perlin Standard brush using DragRect stroke that can be adjusted but we will stick to changing from the center.
You can also reduce the value of RGB intensity, using the slider at the top of the UI, to add more variations. The density or subdivisions of your model needs to be determined at the beginning of the Polypaint process, because subdividing a mesh after painting in a low resolution won't improve or fixed 'pixelated' lines. The texture map becomes tinted with the two colors.
