Occluders for modular pieces?

I am thinking making a few modules to do some R&D on modular level design with UE4. If I use non-manifold meshes, I don’t think occlusion culling would work.

How do I set up occluders for such meshes? (I am guessing visible mesh would be just a regular mesh, and occluder mesh would be a watertight, so to speak, mesh with some special material assigned to it, and both would be exported as one FBX file?)