Small sections at a time
Do small sections at a time, wiping the polish all over the surface. Then buff into the metal until the cloth feels smooth to run back and forth over the surface. You can also hear the polish working away as you rub it in. When it stops making that noise, the area is polished and you can move onto the next section.
For really bad surfaces, repeat the process to get better effect (if needed) as opposed to slathering on too much product all at once.