In PS I would do this by picking a target channel with good seperation between the object I wanted to mask out and making a copy of it, then apply some levels to bump up the contrast and maybe some touchup with dodge and burn giving me a black and white channel mask.
I seem to remember back in TVPaint standard there was 3 buttons next to lock transparancy on the toolbar that would show me the R/G/B channels but it's been gone since I upgraded to pro but I don't know where it is now or if it was just removed.
If I could flip between RGB channels I could copy the channel I wanted to a layer and put that in replace mode and touch it up with histogram fx, or use it as a stencil saving me the trip to that bloated monstrosity that is CS4
![Twisted Evil :twisted:](./images/smilies/icon_twisted.gif)