Level one: filling a shape with random noodling (sketch is on a separate layer and set to overlay - you can use any layer setting you like to make the sketch lighter)
Level two: creating more complex shapes by drawing and erasing
Level three: using “flow guides” in the sketch and use the line to fill in one section at a time. Go back to empty sections and “greeble” them (add details to fill space)
I add an arrow pointing to the “tail” any time I move away from the section where the tail is - I used to spend way too long hunting that bastard down, it’s easier just to draw an arrow pointing at it.
I don’t plan ahead for what will fill spaces, I usually make it up as I go, and will add the same patterns to areas that I think ought to share patterns in common (like how I made all the fox’s feet match in “Silhouette” - the first was just on the fly, but from then on every time I got to a foot I repeated the same motif)
The rest is just having the desire and patience to do this for about a week.
