I've been playing around with multiple-plate etchings and it's an interesting process that yields interesting results. There are many printmakers that use this process to register intricate work with aquatints, overlaying color fields to create new colors from the overlapping colors.
For me this process is a way to experiment with multiple plates each done with a different etching technique, to yield overlapping and varied textures rather than focusing on complex color mixing. The print above was created with 2 spitbite plates and a softground key plate. I like the effect of the spitbite with the linear drawing of the softground plate.
As usual, printmaking leads me on paths to all kinds of experimentation and sometimes I wonder if I will end up settling on one technique for all my work. But, I hope not.