freshen up tired original paint 68 barracuda...

I would suggest some type of cleaner compound. Meguiars makes a cleaner wax that works well. Follow that up with a regular polish wax.

Got two bottles of the cleaner/wax here and it works great by hand, but a lot easier with a polisher.

This is the original paint and it looked just like the Barracuda paint before the cleaner/wax and an hour or less with an orbital buffer.