Render layers and fur.
 

I'm having some problems with render layers and was wondering if anyone can help. I'll explain the setup. I have a video of an actors legs, shot from the waste down. He's wearing baggy shorts creating a shadow over his legs, across the shins.

I want to replace the actors legs with digital legs, they are faun legs. In the Maya scene i have both legs with a fur description and the hooves are separate. I've created geometry for the shorts only for the creation of the shadows on the legs. If i render the scene without layers, it looks great, the shadow is precisely where i want it. I want to render the leg fur, with the shadows from the shorts as one pass without the hooves.

I could just hide the hooves and render the legs but i wanted to automate this. The breakdown of what i want is..

The hooves with separate diffuse and spec.

An AO pass to create a contact shadow between hooves and floor.

The fur pass with the shadows cast from the shorts.

The hooves and AO pass i'm ok with, i can only get the fur to render with it's own self shadowing and not with the cast shadows from the shorts.

If that all makes sense does anyone have an idea how to set this up? Render layers aren't quite as intuitive as i'd hoped they would be.
Thanks.

I should mention one other issue. The shot is 135 frames. The legs don't move but the camera pand right to left. The fur is flickering. Is it just an aliasing issue? The min and max samples currently are set to 0 and 2.