I just draw my spine in and qult the feathers off the chalk line. One big tip I got from Jamie Wallen class was to keep the stem of the feather on both sides point down--when you start doing feathers that curve, etc, I sometimes ended up with one side of the feathers going up and the other side down! So I did as Feline said and did one side and either tied off or echoed back down and then the other side.