At first I used a separate project to perform the imports, followed by exporting to fbx or migrating them. My notes say I made some use of Convert to Blueprint and harvest components to get them in a usable format.
Later I needed to more processing such as creating custom collision meshes, assigning different materials to various parts of the asset, and setting up sockets, so I bought an importer for the 3D modelling program I was using. It was getting a bit silly to stick with Datasmith.