There are some super soft brushes and oils that pros use to improve coppers. That one looks particularly dry, and could be improved by oil. I would leave it to the professionals, or at least get their advice as to what brush to use and what oil to use. I've oiled a coin or two in my time. It really wasn't too hard, but again, you have to have the right oil and the right brush. All I did was put a couple of drops on the brush and then brushed the back of my hand, then I did the coin.
There is a group, Early American Coppers. It is a collector's club. You can contact them and they may point you in the right direction.