To blend the layers, I first created a Layer Mask for the Shadow Elephant Layer and then began to slowly mask off the shadow areas, allowing the Highlight Elephant Layer to show through where appropriate. I used a blurred brush set at different opacities to reveal the highlights in subtle, blended manner.This is where masking is invaluable, allowing you the freedom to experiment, start over, tweak, mask and unmask to your heart's content.The key is to study the lighting of other objects in the scene, and then match this to the elephant. When done right, it can be surprising how effective this technique is in recreating the fall of light and shadow.