Without adding further paint I used the brush edge on to make linear marks at all angles around the swirl alternating between areas of the painting so that I picked up paint from the dark and added to the light, and picked up paint from the light and placed in the dark.
Next onto a small brush to put the detail at the focus of the eye and the shrubbery tunnel. The balance of light and dark and colour here is key to perception of the finished picture, and worth spending a little time on. Note how the light bleeds into the tunnel - the way to do this is to carry on using the brush having deployed the paint, working away from where you put the paint down. I used this technique particularly for the bottom of the tunnel.
The last part of this picture - the detail is a bit repetitive, but doesn't require much thought, so feel free to let the brush do what it wants and work with it. I've used a long thin brush here, and with each colour in turn made masses of marks to represent the twigs of the shrubbery, making sure that sufficient colours are used throughout to give the perception of a tangled depth of vegetation. Each brush mark took a fraction of a second. You should be able to get half a dozen marks or so for each loading of paint - but don't overload the brush as you'll get a big blob thats awkward to do anything about. Once satisfied with the shrubbery I've blobbed on tiny spots of red for the berries (its an Autumn picture). One more touch for completion - I went back to the large brush to push patches of green grass into the foreground, using two shades of green to provide variation.
You may have spotted two posts in the reference photo. I decided to leave those out as I find they detract from the composition. Never be afraid to leave things out, exagerate things you like (within the limits of credibility), or use your artistic licence in any way to improve the final composition.