Typical process:

1) Completely disassemble.
2) Small parts, jockey wheels, nuts, bolts, springs, etc. go in the little ultrasonic with some Dawn and water.
3) While they're buzzing around I take WD-40 and several different types of brushes to completely clean the RD body and cage plates. Sometimes I'll lightly polish with Mother's...lightly. Although it usually works out that the WD-40 and some rubbing really get them looking very nice.
4) By the time I'm done with the body and cage plates the small parts come out of the ultrasonic and are rinsed and dried.
5) RD reassembled lubing and greasing where appropriate.

I can do a whole RD in about 20 minutes if I'm lackadasical...if I really get going four an hour.

Of course there's a limited amount of disassembly you can do on a FD.

I honestly believe they're as good as new or better when I'm done with them.

EDIT: I also sometimes buy broken examples just for parts. I have a bag full of pivot springs, jockey wheels, cage plates, etc. When I can I replace more worn parts with less worn. Especially jockey wheels.