Here is the way one painting, Fire in the Snow, part of the Egypt series, evolved.

quick sketch with vine charcoal
quick sketch with vine charcoal
underpaint with complementary color
underpaint with complementary color

if you start with a color's complement, the top layer will be more vibrant. I know the sky is going to end up in the pink-ish range, so I start with green-ish

blue flames to start
blue flames to start
block in branches
block in branches
red eyes start green; yellow start
red eyes start green; yellow start

purple

more branches
more branches
orange-y warmth under blue-ish snow
orange-y warmth under blue-ish snow
heading towards a final color
heading towards a final color
here comes snow
here comes snow
some warmth on the horizon
some warmth on the horizon
flames!
flames!
warmth in flames
warmth in flames
sketching in trees
sketching in trees
starting to paint trees
starting to paint trees
more trees...
more trees...
and branches (and second moon)
and branches (and second moon)
rock outcropping appears
rock outcropping appears
smoke...
smoke...
refining foreground snow
refining foreground snow
the egyptian owl ...
the egyptian owl ...
gets refined...
gets refined...
and more refined
and more refined
the snowy owl starts to emerge
the snowy owl starts to emerge
painting owl feathers
painting owl feathers
more feathers
more feathers
and more feathers
and more feathers
and more feathers
and more feathers
and more feathers
and more feathers
and more feathers...
and more feathers...

I spent a month just painting the feathers on this one bird. Then I decided he or she needed a different face.

The finished painting
The finished painting

I didn't photograph every single stage, but enough of them so you get the idea. I worked on this painting over the course of about five months.