One possible way would be to remove the casing, unsolder the battery terminals then proceed to remove the black coating with 1200 metal finishing paper, ensuring the same direction is maintained from start to finish. When all the coating has been removed change from 1200 - 2600 finishing paper and continue to smooth & polish. Im NOT convinced you would get the same finish as the one pictured as chemicals replaced the sanding to give it a floating surface, hence the Mirror Finish. I personaly think unless you know what your doing it should be seen as a remote control unit and not as a blank canvas. it could be expensive!
Many Thanks Andy