Link to Joe Real's Bark Grafting Tutorial
This link should get you to the tutorial, but you'll have to register with the Citrus Growers Forum. I did and have never experienced any problems from it.
After gaining access to the site you'll find links to propagation of citrus, one of which actually is Joe bark grafting a pear. Very thorough, very helpful, nicely done and easy to follow.
That said, bark grafting is, for me, limited. I find that it works better on younger wood and probably better on pear than apple. Maybe I just have a tough old apple and tender wittle pear.
Here is a link that might be useful: Joe Real's bark grafting tutorial