When negative painting, you sort of 'underlap' the layers. That's the word one of my fave artists, Linda Kemp, uses. It means you can build up a really complex and patterned piece of work.
Here's the progress on the "Jenny Wren" painting so far:
And the "Rainbow Plants" was a bit dull in the background. It lacked contrast, so I punched it up a bit by adding background light, again using negative painting.
Now I just need to add another drawing layer to these, and can call them finished. Hopefully. I have such a hard time deciding when a painting is finished.