Shelling is possible, but not automated.
You can delete a small part of the mesh to make a hole. Then Copy, Scale down, and Reverse to make the inner surface. And finally there is a command "Stitch Holes" that will join the two surfaces with new triangles.
Of course this depends on the original mesh being a single continuous surface, and being able to shift the inner surface carefully to get the required width without accidental self intersections.