"He who marches out of step hears another drum." ~ Ken Kesey
Split fountain?! Come on Andy, you're dating yourself
In illustrator I always duplicated the image so in this case you would have three copies. Decide which color you are doing and changed the other colors to white and the color you are working on to your spot color. Then to extend the gradient sliders farther out for each color so that you get overlap and minimal shirt showing through. How much is something I just do by eye and it really does not take long at all once you have done it a couple times.There could be a better way but this is how I handled it.