Righty ho
I start with a black undercoat.
Step 1. Paint all the uniform areas Desert Yellow. I've used GW and Vallejo for this and both are good. Leave to dry.
Step 2. Paint blotches of Vallejo Luftwaffe Camouflage Green and Beasty Brown. Don't go too mental with this, there should be roughly equal areas of the three colours with no green or brown next to each other. Leave to dry.
Step 3. Wash with Devlan Mud. If your a fan of dips that should work too. This softens the edges and pulls it all together. Leave to dry.
Step 4. Take each colour in turn and mix with a little white so you get a lighter shade of each. This is the fiddly bit, highlight any creases and edges with the appropriate colour. Again less is more here, don't over do it.
Your done!
There is now an optional step 5. You can add small dots of Bleached Bone on the green and brown areas to give you the spot camo affect. Again, restraint is needed here, a little goes a long way, two or three dots per area will do.
Hope that helps.