We were experimenting with the drum plucker and only doing 6 ducks, so, here's what I learned...
1) Two ducks in the drum worked fine - she had a water bath big enough for two at a time. There was still quite a bit of hand plucking, more than I expected.
2) We tried one duck in the drum, it would not roll around well enough and the top didn't pluck well.
3) We tried three ducks, left them in the scalder too long and ended up losing body parts (heads and feet) and tearing up the skin a bit. I'm not sure why we lost body parts like that, probably too much in the scalder.
All of them required more finish plucking than I expected. We saved quite a bit of time (usually it takes me about half an hour to slaughter, scald and pluck a duck, it took me about that long to do that AND butcher it), it wasn't the cure all that I'd hoped, it was still work! I'm not a speed bomb in the first place and working without my kitchen to butcher slowed me down. We averaged less than 30 mins per duck start to finish - I guess that was pretty good, as we weren't that organized.
I'm interested in trying the plucker that runs off a drill. I'm thinking I'll have more control over what part gets plucked and not miss parts of the duck. Also it's a lot more reasonable than a big drum, not that much more than the gas to drive to my friend's place to do them.