all I ever did was put a stump in the vice, and use two screwdrivers, reversed so I had a handle in each hand, pinched it and pulled. Just like a stripper. In fact I have a stripper in my taxidermy shop and actually like the screwdrivers better.
A couple of things though, if they've been frozen a while... quick thaw them in water is a good start, then inject water with an insulin syringe along the tail to get fluid back in the tail... if its freezer burned in there you'll have heck.
Start the skin down with a razor or scalpel etc.... get it kinda going and then sometimes it takes a bit of pressure to get it going with the puller, like a lot... but once it goes back off a bit. Sometimes just bumping it down the tail works too.
The fox will be more fragile as noted, what I've found with them is that once it goes its all done at once, good or bad.
You can get salt/tanning solution in a tail without splitting it but its very hard to do....
