Not that I'm an expert by any means, but I used a mop wheel that I could chuck it into an electric drill to do the rough working in and shaping, but the finishing part was all done by hand with 150 grit, then stepping down to 22o grit.
Like the other guys have said already, it eventually comes down to good old fashioned elbow grease.
I did use an electric palm sander on the belly of my limbs to get them nice and smooth. I found that the flat surface of the palm sander made it easy for me to keep it all even, I alse employed the help of a small palm sander with a triangle shaped head for the smaller areas where the bigger palm sander couldn't get to. That was a nice break from rubbing and scrubbing, but don't get to crazy with that cause you can take off tiller in a hurry with it if you aren't careful.