The scheme is based around a triad of Games Workshop paints from the current range which are used for the skin:
Base - Deathworld Forest
Layer - Straken Green
Layer - Ogryn Camo
Although there are three paints that make up the skin (four if you count the wash) it can be done very quickly. Once the base and wash are dry it takes me approximately 20 minutes per model to finish the skin.
Firstly, undercoat the model black and slap the Deathworld Forest on with a tank brush. I found that it didn't even need to be thinned. Once this is dry, smash the life out of it with a brown wash. I used Devlan Mud (which is from the old Games Workshop range). The model should end up looking like this:
Here is a bonus picture: 40k cat stops play. A regular occurrence in the Wargarage, though she can usually be convinced to sit in an empty box and watch.