An electric random orbital buffer will make this job a WHOLE lot easier. Reducing the swirly marks takes a LOT of elbow grease and you will probably run out of energy long before you'll make much of a dent in the swirls.
I have a Shadow also and it's very difficult to keep the scratches/swirlies away from it. But I have found that with enough patience and the R/O buffer I can keep it looking fairly presentable.
I have also not tried this yet, but it may be worth a look:
Attachment 13788
Black Box - Turtle Wax
As you have probably seen by now, these cars aren't truly black, but a very dark cherry color. If I try this, I'll do it in an inconspicuous spot in case it looks funny
