You're only option is re-paint (shop or rattle can, however you choose). The clearcoat is gone in some places and no amount of buffing will bring it back. Even if you were able to polish the basecoat into something presentable, it would only last for maybe two months because there's nothing to protect it from UV rays (thats the job of the clearcoat).
If you did want to repaint it, you don't have to go down to the bare metal to do so. Most primers can be laid over other paints so long as the paint clean, already bonded well to the bare metal below (i.e. not peeling off), and scuffed up enough to allow the primer to 'grip' on to it. Scotch brite pads work well for that.
If it were me, I'd scuff the whole car. For the spots that needed it (paint flaking off, rock chips, rusted areas) I'd go down to bare metal and feather out the edges.
Then I would primer the entire car with a high build primer and block sand that. Then shoot with a dupli-color lacquer.
I've used
this from Duplicolor on two cars and it worked good. Kind of idiot-proof. It's a ready-to-shoot lacquer that sprays out of pretty much any gun. I've used
these cheap suction feed guns and gravity feed guns to do the job.
Even has a demo video:
e/Learning :: Paint Shop
And heres someone's review of it:
Painting with Dupli-Color Paint Shop - Tampa Racing
The best part is theres no re-coat window. So two years down the road, you could scuff the car again and lay down another layer of clear (if it needed it). Then wetsand and buff to a smooth Autopian finish. And you could repeat everytime you felt the paint was too thin from buffing/polishing and needed more clear.