I tie lots of flies and have recently preserved some neck hackles and saddle hackles by scraping all the fat I could off the skin with a flexible scraper and rubbing the skin side down with some dishwashing liquid diluted with 6 parts water. It helps to rub the soap in with a soft bristled toothbrush. Try to keep the soap off the feathers as much as possible. Rinse the skins with cold water, blot dry with paper towels and sprinkle with a liberal dose of Borax on the flesh side. I let them sit overnight with it on and in the morning I checked for damp spots. If there were any I put more Borax on the area and let it sit for a day or so. Then just brush the borax off and leave the hides to dry and cure for a few days before storing.