Want them soft then soak in a bucket with some Tide or Dawn Dish soap. Use warm water if they have the bone in then remove bone by splitting the tail with a sharp knife down the center of the white and remove the bone and hang up the tails on a cloths line. When almost dry cover the backs with 20 mule team borax. Lay flat untill completely dry and you are set to go. At least that is how I do it and have never had any trouble with it. The Soap will brighten the color and the borax will preserve the hide.

Redman