Buy a few grades of wet sandpaper and some Blue Magic polish like I assume you've read about. It's almost impossible to mess up. Just practice on a spare aluminum part or even the bottom of your stem. Those levers would only take a few minutes, just don't get crazy with the rough grade over the Campy etching. I've polished up seatposts with deeper scratches than you have and it took about 10 minutes.
After you polish your first part and see how easy it is and the results you get you'll want to polish everything. It's addicting.