How to get the ghosties to appear on cue?

Volume Volume volume.

You have 37 spirits available etherally stringed to that buiding and also be near a cemetery and rely on the show times to coincide with the wobble of the earth's magnetic grid, so twice a day there is a wave of activity. At Jims latitude the grid sweeps about 43 miles back and forth and he is in a dead zone for other interference like cell phone and radio signals.

Oh, yes and Jim is actually dead too. And he passes a lots of gas that things can be projected onto.