I think I know what you mean, when they are around 15-20 weeks they can have a LOT of pinfeathers starting to come in that you don't notice until you begin to pluck. I process a lot of standard & mixed-breed roos and usually wait until they're 20-24 weeks to butcher. They're meatier at that age anyway. And I've learned to check next to their skin before beginning, to see if they're hiding new feathers ready to sprout. If so, I may let them grow out for a few more weeks and avoid all that hassle.
Otherwise, if you get a good scald and have them hanging by the feet so you have both hands to use when plucking, it shouldn't be too much trouble to pluck. The regular feathers almost wipe off the body like cleaning the lint trap of the dryer, and you can scrape most of the pinfeathers off with a butter knife.