Pete,
The borax method your describing wont really work. The reason why is that you MUST get the bone out of the entirety of the tail. The bone holds grease, oils, and of course flesh which is all subject to rot and eventually degrade the hide making the hair fall out, not to mention smell.
If its only been a year or two and it was put in the freezer quickly following the kill then it should be good. It needs to be completely deboned, fleshed and tanned. Bird wings/flesh is much thinner, more absorbant, and readily accepts chemical treatment such as borax. Coyotes are carrion eaters and therefore contain much more bacteria that needs treated through the process of pickling and tanning. Skinning it will be the most difficult part for you, slit it right up the middle on the underside of the tail. Go very slow, take you time and work around the bone of the tail, cutting it away from skin with a small blade. DONT try and pull the bone away when you get to the end....even tho they look like they will come away easy from the skin they will inadvertently tear and pull skin/hair away/out of the tail. Give me a call if you need any help, would gladly walk you through the process. Best of luck.
Joel- BRT