Gary,
You got it on the sanding! Maybe add 400 in there. The goal is to get the ripples out of it without sanding through the Al around the edges. So take your time, use the paper wet. Don't get crazy with the 320 or 400 around the rear edges of the tail cones. You can also use a very small amount, very small, of polish on a rag. Then apply it where you want them darker. Oil, grease would work too. Then wipe them off as much as you can with a cotton rag. This will be almost un "smudgable". If you don't like the effect, just rub it down with the 1000 grit again.

As terry said, you could get out the airbrush with some flat black. Spray the panel lines lightly, then come back with some 800-1000 grit to remove some of the black and to fade it a bit.

Now are you sure that was the dog drooling on the tail cones??