If you are using a plucker we find the temp is more picky. Too hot and the skin is too tender and the plucker, when the rubber fingers are cold, rip the skin to shreds. If you are hand plucking, you have a bit more leeway as your hands will not rip the skin so badly.
This is Hub's method. The water is NOT boiling! HOlding the bird by the legs he dunks and swishes, then lifts it out of the water for a few second, repeats this about 3 times then does a test by yanking the largest wing feathers. If they come out easy, we're good to go. IF they require quite a bit of tugging, back in the water for a few more swirls. Start with fewer, shorter dips and progress to slightly longer dips if you find the feathers are not coming out easy.
Since these are not actual meat birds, they may be somewhat harder to pluck, keeping in mind that meat birds are designed for ease of plucking, and other birds are not. In that case it may take a bit more hot water dipping than for meat birds. GOod luck!