The best thing I have ever seen on fur handling was a DVD that I bought last year from www.allpredatorcalls.com
it showed every detail on about every animal. Practical Fur Handling is the DVD you want. Over 5 hours of how to, but you can skip whatever you want and go directly to what applies.
Coyotes are a bigger challenge and make for better filming for DVDs. Easier marketing, this drives the desire to call them, it looks so easy on video/DVD. Here in the east where we are, they are a true trophy due to their lower population and tougher habitat to call. Fox are more plentiful but harder to video in this habitat that we have.
The fur market has dropped alot over the last couple years. it fluctuates alot. People hunt what they have, not what the fur market dictates. I personally prefer fox because of the mere numbers and fast action. Although I wouldn't pass up a coyote if he came to my call.
If you are in it for the value of the fur, then get some snares and leg hold traps and get after it. More volume, less fur damage that way too. Otherwise just appreciate and enjoy what that mouthcall brings you and take pride in fooling them.