Soaking in salt water won't loosen the feathers. Scalding works by heating the skin and softening the tissue that holds the feathers in.
When my DH and I butchered turkeys, we hung them upside down immediately after killing, (DH walked up and shot them in the head, which might make a difference as far as how easily the feathers come out, I don't know for sure) while still warm, and started dry plucking. With both of us plucking, we had the turkey mostly plucked in less than ten minutes. It worked best holding the bird still with one hand, while yanking out feathers with the other. The larger feathers, like the tail feathers and wing feathers, don't come out as easily. We brought the bird inside and placed in the sink. Then I poured hot water from the tea kettle onto the areas that still needed to be plucked. I scalded and worked on one area at a time, (like just one wing, then the other wing, then the tail...) I used pliers for some of the big feathers that were still hard to get out.