The science of mixing clay is an entirely different beast altogether and we are nothing but kids lost in a strip club. We are absolutely clueless regarding the optimal composition of clay and found a working formula by trial and error, and with a lot of help from others who came before us. We also used a measuring cup, which measures volume, whereas clay is usually measured in weight. But it worked. (to some extent, our clay artefacts are still prone to cracking, and we were not able to fire them in a kiln: instant crack)
Here's the formula:

• 400ml water
• 400ml Grog
• 400ml Kentucky Ball Clay
• 400ml Silicone 325 Mesh
• 400ml EPK
• 400ml Custer Feldspar
• 1 bottle cap of Darvan 7 (or 175 +-10 drops)

You would want a less viscous mix (more like a clay slip) so it can move through the hose effortlessly. We also used photo lights (flood lights or heat guns work as well) to bake the prints while they're printing, to decrease their drying time and increase stability. With this method, we were able to achieve a maximum angle of about 30 degrees, after which the artefacts started collapsing.

If you're in the Bay area, the ingredients can be purchased at Ceramics & Crafts Supply, which is located in SOMA, San Francisco.