Here are a few drawing I made to try to get to some rough lines for a panel.
I found that really not sticking to any fixed process also helped in some places. For example i would draw a rough layer and keep only part of it while roughing a new part. I did tend to find roughing in blues and seeing how that worked in dark worked pretty well (i would have the blue opacity cut down so i could see the top drawing more clearly). At end I change the opacity of the dark line to put things i dont want to focus on (make it lighter -- like background) and things I want to focus on (make it darker).
Check out the amazing story boarding work by Jeff Biancalana (gatodiablo dot com) and Ben Balistreri (benbalistreri dot blogspot dot com) to see some beautiful examples of the lights and darks to tell story.