I've got a drill driven pump, two pieces of garden hose, and an adapter that screws into the valve stem.. works well. You jack up a rear wheel, drain the air out of the tube/tire, then remove the valve stem core (if it has a tube, the whole centre part including the core will come out, leaving a larger hole for the water to go in. Screw in the adapter on one of the hoses, and you're ready to go. I built my own adapter, they should be available commercially too.
Rotate the tire so the valve stem is at 12 o'clock, then start pumping water in. You'll have to stop a few times to bleed excess air out, simply unscrew the hose from the pump, or the adapter from the tube, and let the air out, then keep pumping water in. Once you start having water coming out the valve stem, the tire is at 75% full (to the 12 o'clock position of the valve stem anyway), then top it up with air to the pressure you want. Mine takes about 20-25 gallons of water (or whatever fluid you're adding) per tire.
Sean