But if you needed to make an material like the one i showed above where its not a uniformed color or the ones you have in your images, which looks nice btw. Wouldn't you have to start mix and added stuff together to get the correct reflection where there are paint and where there are rust for instant?

Are there no way to get refraction in the physical shader? I haven't really tested a lot of glass or water using it, but agree it weird that they haven't added such channel to it.