There are some pretty impressive scratches, dings and dents in your GMT - it’s certainly developed a distinct patina and character over its lifetime!
You’ll struggle to get the deeper scratches out with Cape Cod. It’s an abrasive polishing cloth, but there’s a limit to its magical capabilities. It’s more effective on dealing with light scratches and swirls. You could give it a try, but it’ll take serious elbow grease to polish some of those marks out.
You may well need to use diamond files and sandpaper to remove the worst scratches before getting to the stage where Cape Cod is going to make an appreciable difference.
Removing some of the dings is probably not even possible without removing a significant amount of metal in the process. You might be better off leaving them, to show that it’s a well-worn watch that’s had a very active life.