I've been using a small fountain pump, connected to a 1/2" poly hose that can be stretched to accept a garden hose female connector. Then I use a garden shut off valve on a watering wand.
You can use a larger pump if you want, find one that sucks from the bottom if you want to empty your watering rez. I like the low flow to slowly saturate, but then again I'm only dealing with 4 plants.