Another foot note, get an old distrbutor shaft and make an oil priming tool out of it. You can install this shaft in the end of a drill motor and stick it in the engine into the oil pump. Turn the drill on and you will build oil pressure this way. Watch your gauge as you are doing this. The oil pressure will come up slowly.
Just a side note on this. I personally like to remove both valve covers when doing this so I can visually check oil flow to each and every rocker arm. This can be messy, but is cheap insurance. When I was building alot of engines I actually purchased two new valve covers from GM and cut the tops off so I could check the oil flow without the mess. Also, JEGS sells the oil priming tool JohnZ mentions (different brand) for less than $20.00.