Are there any tutorials/information about converting a shader for use on Unity terrains?

So I have a shader which displaces the vertices based on the red pixels from a Texture. I originally wrote this for a terrain to create tracks and footprints etc. but it turns out I can't just apply any shader to a Unity terrain.

I've found this tutorial - https://alastaira.wordpress.com/2013/12/07/custom-unity-terrain-material-shaders/ but I'm wondering if anyone else has other links containing more information and specifically information about what the differences are between a "normal" shader and one written for a Unity terrain. Also any info about performance and efficiency would also be great. To be honest anything about writing shaders for a Unity terrain would be awesome!

thanks,