To be honest I've never looked at a pressure gauge when priming, the way I've always had them hooked up they aren't powered during cranking. What blomb said sounds about right, though I'd probably not let the fuel pump run dry. If I've had a motor sitting for a while I usually crank it a bit with no bang (protip, you can make the Subaru ECU supply 0 fuel during cranking over certain throttle percentages, I think the default DBW ECU maps have this). Another quick way to make it not run is to unplug the crank angle sensor.

Once I do that I start it for real. If it doesn't get "real" cold oil pressure (~30 psi depending on motor) in a few seconds I'd kill it and figure out what's going on.

I'm sure there's others here that have a more detailed procedure.