I used a fine brush to paint the liquid latex at random on my watercolor paper. The result was a network of negative space, over- (or under-) laid on the black-ink network I had previously drawn.
I started on one end of the paper with Permanent Green #1 and at the other end with Aureolin Yellow to get a graded wash.
I filled in the negative spaces with red on the green side and purple on the yellow side, with a few variations. I did save a few loops to fill in with solid colors.
Perhaps with a little more planning I could design a pattern of filled-in loops that would act in counterpoint to the mass of squiggles in the rest of the composition.