Hi all, i've read often about the control wich a multipass renderind give on the image.
Technically (if this is not correct let me know) you can rework in a 2d software (zbrush or photoshop or whatever you want), your image split in multiple layers; in this way you can play with different part of the image...
I've read somethingh about this technique from a thred start from Meats Meir: he render one time the shadow of the whole image, and then work on every single layer and composite all after , avoid everytime rendering the whole image.

I would be start a thread where put all the info about this technique:
how achieve from the current work the alpha layer( layer used after in photoshop like mask)
Tips about the antialias around the image in photoshop(avoid contour line when your background is different)
How do you use this layer in Photoshop;normally we have a layer for the shadow, for the specularity, diffuse........
If possible puts some reference or example pics

Thx
Bye
Leo