Here’s another quote from Bill Garnett. (yeah I’m a big fan) “Take your own painting and treat it like a painting in a museum: make variations on it, analyze what’s making it work, find a structure.”
So, at the risk of sounding overly self-satisfied with my recent progress, I’ll take a stab at doing just that.
First off, here’s a nice sun lit picture of the painting as it is right now:
(click the thumnails for bigger images)

The tree in the bathers painting uses stacking of flat shapes and value shifts to open up the space in the center of the composition. This is a stacked construction.
(click the thumnails for bigger images)

The stacked construction is placed over an under painting of overlapping glazes. Those initial glazes are varied in shape so that together they form an interlocked negative space between the figures of the painting. (Note that I mean negative space and not neccesarily ‘ground’. This acts in concert with contour continuation throughout the entire composition to create a sense of synthetic space.) These shapes are glazed over one another darker and darker to push the space back into the picture plane.
(click the thumnails for bigger images)

The stacked shapes of the tree step back in value as they cross over the overlapping shapes of the under painting so as to seem to receed into the darker center of the glazes. Ok, this is hard to describe, but it seems useful to try. The location of the steps are shown in the pencil sketch above with thick black lines.
The result is a tree that seems to lean back away from the picture plane. Surface elements have then been added to interlock the stacked construction in a manner that implies a continuous flat shape flush with the picture plane. These flat interlocking surfaces fight the receding stacked construction creating a tension in the complete figure.
These three techniques could be applied in a thoughtful manner at the outset of the next painting. An initial sketch of the relation and continuous contours of proposed figures and negative spaces would provide direction for the placement of the glazed backgrounds. A second sketch would layout the stacking constructions and would provide a basis for the the overall value composition. A third sketch would suggest a means for interlocking and resolving the figures. The three sketches could be done on velum and viewed on a light table. This would guide the whole glazing and construction process much more efficiently than a single sketch of the finished surface.