cleaning a ballscrew

Just acquired a few ballscrews from a friend , and they are in
desparate need of a good cleaning.
Whats the best way to clean them?
Is it possible to soak them in oil or WD40 to loosen up the grime
inside of them, because i would rather not take them apart.....I'll
probably never get them back together if I do.
Also, what should I use to grease them up once cleaned and ready for
use?
I have those rubber boots that go over top of them to keep out dirt
and such from getting in the ballgrooves.
Regards,
Jim