Began with equal parts of GH at a very diluted concentration.
This week, I increased the concentration to the manufacturer's recommended dosage for seedlings (1/4 tsp per gallon).
@TomatoloverBoy, I found this: http://420dotcom.com/aeroponics-diy-easy-aeroponic-system-build.html helpful for sourcing equipment and getting a sense of what I'd need.
I went to a hardware shop to find the hard plastic tubing and fittings I needed to deal with the pressure.