Hi Mat, the problem with Photoshop for this tak is that everything you do is permanent, so you need to copy a layer before apply any effect.

I use Hitfilm for that task because everything is realtime and I can change things all the way.

Some tricks you cam performe with Passes:

Add a Ambient Light (about 5 or 15%) and render Ambient Occlusion, will give you a better depth and more faster them Sky Light itself.

You can decrease the Diffuse channel and use more AO or GI as diffuse

You can blur the shadow or decrease the amount (value) to get more clear objects

If you want to "mask" objects you cna render the Object Index layer, that will color every object in a very easy way to select them

The good thing about passes is that you can change values for every layer and make your image more clear, at same time you can apply effects to some layers and get a new image: duplicate your reflection layers, blur it a lot and add at the top of the other, you will got some glow effect very easy.

For users of Photoshop full (not like us that use Elements), there are good plugins for DOF using the Depth leayr also.

here is video that show a simple trick with SSS, without render SSS:

http://www.youtube.com/watch?v=VvobExKzMxU

Follow me at euQfiz Digital