If you're doing a "shoeshine" job with hand held emery cloth instead of using a powered belt polisher, be sure to do a thorough cleanup afterwards. Any leftover abrasive material plus motor oil makes a good grinding compound that will trash the new bearings in record time. I spin up a crankshaft in my lathe at low speed and use an ultra-fine grit sanding belt powered by a small angle grinder motor to polish cranks. Some machinists insist that the direction the polishing is done makes a difference, but that's not a factor in hand polishing a bearing journal. You don't need to remove the crank to polish main journals- - - -just roll the upper bearing shell out and slip the polishing cloth through the gap the missing bearing leaves. Use lots of spray brake cleaner and an air hose blow gun to flush away any leftover grit.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!