No, there’s not a simple way to blend materials on top of each other if they aren’t specially set up for that.
The best option is probably to draw the mesh/es as normal, and then re-draw them again, with a different translucent material applied, and make that material push the normals of each vertex out by a centimeter or so.
Note that you will get “cracks” in the shield along hard edges, unless you stitch said hard edges with degenerate triangles. For most organic meshes, this doesn’t matter, as every edge is smooth.