Currently, the rules are that extruded and revolved meshes can’t be used for compound parts so only surface partitions can be used (unless you mesh each part separately and then connect them with tie constraints). On the other hand, transfinite meshes can be applied to compound parts so you can use volume partitions to obtain proper regions (parts) for hex or hex-dominated meshing. Another rule is that each volume (region) used for transfinite meshing must have 5 or 6 faces with 3 or 4 edges each.