I think you are referring to the basic material setup that happens when you import assets. What happens is that the mesh is allocated a “personal” material based on the mesh and texture names.
The best suggestion I have is to have a look and learn the basics for setting up a simple material. It may take an hour or so, but will make sure that all assigned materials are optimized for each mesh. Depending on the complexity of your scene, it’s likely that you will have to go back and update materials to material instances.