When using a standard 'Unity Terrain' object, textures can be tiled, layered and masked using a method called 'splat mapping'. This technique is ideal for texturing terrain, however when creating a custom terrain object in a 3D modeling package, such as a floating island that is not a flat object (like a unity terrain), but is a three dimensional model, the splat mapping method is not available to use.

What are our texturing options now?
A custom UV map could be generated and applied to the model, however all detail will be lost when zoomed to the level of a terrain, as even a 4k texture map will more than likely be too small and distort.
Another option would be to create a single seamless texture and tile it over the model, this will work fine, but you are restricted to one texture, and one texture only - creating a bland look and feel.

Or, you could use a custom layered shader that simulates the 'splat map' method, which can be applied to any 3D model.

- perfect!

 Tutorial introduction
Launch Video (1m 22s)

 Preparing and exporting mesh from maya, creating a layered shader
Launch Video (3m 42s)
Layered shader used in tutorial: here
Other terrain shaders: here

 Setting up and applying the layered shader, includes creating an alpha mask in photoshop
Launch Video (9m 48s)