We experimented with printing electric paint through our paste extruder, into a Fractal Antenna shape recently. Through trial and error, we managed to get it fairly well figured out, and we wrote up our experiences here:
http://www.structur3d.io/blog/2014/7/1/printing-a-fractal-antenna-with-bare-conductive-electric-paint
If you want a paste extruder, you can build one from this design rather cheaply: http://www.thingiverse.com/thing:20733 - Includes a rather easy way to quickly change out filled syringes and uses the same luer lock system that this kickstarter does, and is available now. Also won’t cost you $300.
The Universal Paste Extruder is cool. But it’s also good for someone to make a productized option, for people who want that. The pricing isn’t bad, for what you get…
I like this paste extruder design more than that one. http://www.thingiverse.com/thing:181833