If you have no experience with a buffer I would NOT recommend just giving it a try. You may remove the scratches you are going after but trust me if its your first time you will leave hologramming, marring, or more swirls. Odds are you will make it worse. In fact if you are attempting the rotary for the first time I would guarantee it turns out worse.
Clay barring will do zero for removing the scratch. It is simply prep before you polish. Always start out with the least aggressive that you would need. Can you feel it with your fingernail? What you use all depends on how hard your clearcoat is and how severe the scratches are. Start out with a hand scratch remover like ScratchX or Meguiars swirl remover. If that doesnt work, which it probably wont… step up to the rotary…theres so many different polishes and aggressive pads, its hard to just explain it all. We can do it for you if you would like.
If you want to just hide it yourself…3m imperial hand glaze topped with collinite 845 you wont know its there for six months. Available from carquest or most other places