Hi shadowgin,
There are some option, but I guess the most usable is: Mesh> Transform Tools> Normal Move. [While all Polygons are selected]
If the copy would be scaled as one, all parts move away from the origin (axis) which is not really the way to go. With the Normal Move this works per polygon in “Normal” direction.
The limit here is the smallest Polygon-size in “corners”. If it is moved more than that, polygons inside of such corners will badly intercut. Perhaps normal move the original in one direction and the copy in the other direction to gain more without running into trouble that fast. Perhaps then scale both a little bit globally, the Object Axis of the face should be in the “head-center” for this.
As a side note, if you use [additionally] the “Smoothing Deformer” for the inside copy, it might look even more natural, as the smaller it becomes, the less details one expect, of course with a thin one—not so much, but the smoothing will help to Normal Move to the outside as well. I’m suggesting this here, as I have no idea about your target. Different layers for different light absorption and colors…?
(A Plain Effector could be set to point deform and P.Z. With a Restriction Tag one could “paint” a Weight Map on the new surface, to limit or add movement in certain detail areas, while starting with a 50% weight. This comes close to Sculpting of course.)
All the best
