I wanted to experiment with the very popular style of making a monochrome illustration from a black and white value painting. But I wasn't really satisfied with the results and it got complicated. Finally I just solidified the gradient map layers and worked at it from there. Still I think using values and the gradient map is a very good way to start an illustration. It gives a simple foundational color palette which is easy on the eye. Nice and simple. Then you can tweak it with a few extra colors. Obviously this doesn't work for all intended illustrations, but it's a very nice technique to have in the toolbox.