Right heres what you must do to preserve a fox skin for using as a decoy or just to have hanging around so it wont fall apart.
This process is fixing the skin, it is not fully tanning, but it will preserve it and you will be able to use it.
One fox skinned, remove all fat, gristle, sinew from the skin, scrap it all off, pegged out if you like. If you cant finish it in one go, throw some good salt over it, and continue the next day, but keep it in the cool.
Finish off scrapping, take the skin and wash it in warm soapy water to get all the crap out, rinse in cold water until clear.
Plastic dustbin, 7 galls of warm water, 7lbs of good salt, and 7fluid oz of Formic Acid, stir it all in until clear. Dump your wet skin in there, and stir it and punch it out into the liquor, go back every hour and stir make sure no air pockets are under the skin., and use wooden broom handle to do this, not metal pole. Make sure you put a small stick down tail so as to get the liquor inside otherwise the tail hair will fall out. Wear Rubber gloves.
Leave in there for about 2 days, take it out drain off, and peg out on board, when it gets near to drying, scrape again, sandpaper or whatever, take off and rub clean hardwood sawdust into the hair and then tap out and blow out with hairdryer, this plumps up the hair and puts a shine back on the hair. Thats it, one fixed but not completely tanned Fox skin, and the hair wont fall out.