Gesso and sand the alien head.
Gesso Alien

Three layers of gesso on the alien, sanding between each coat, to prep it for

Smoothing the bird sculpture with sanding and joint compound.
Smooth & Fill

I waited two days for the clay to dry on the beak and eyelids, then

Filling and smoothing concrete paper clay with joint compound and gesso.
Fill and Smooth

Added a thin coat of joint compound and gesso sanding between layers for a smoother