Last month I was commissioned to separate a couple of designs for upcoming movies. Nothing difficult as far a separations, but very flattered to do so. Each were about 10,000 shirts for the initial order.
If you are interested in learning to do do this yourself without a software program that cost a lot and can't compare to what you can do, then download the book to guide you as you learn to do manual color separations in Photoshop Channels!
