I don't know how useful this tutorial will be, but I had it on the back burner for a long time, so I thought that now would be a good time to finally post it up. This is a nifty shop trick I learned after spending plenty of time perusing CS5 for hours at a time. This is primarily for people who scan in their lineart from paper rather than draw it digitally. But I suppose this system could also work for digital users who want to get smoother curves. I used Lady Oil for this tutorial. Feel free to download it if you'd like!
Question!! How do I make the channel(s) into gray only?
You can change the channels into grays only by going into image>adjustments>grayscale and that should change the picture's settings to grayscale.
There's one question I have about this: Does that work-path method need to be done for every individual line? Or is there some kind of batch process?
It's works as a batch process. But if you want, you can use the quick mask and erase certain sections if you want to work on individual lines.