Rebuilt Engine

Hi List

I've just completed assembly of the chassis / drive train of my 1957 TR3. 
Yesterday I turn the engine around for the first time using the starter 
(no ignition yet) and my question is: Am I right to worry not being abel 
to get oilpressure readings during this short, slow RPM turning?

Is there anything I could do to ensure oil is transfered through the 
system?

Kind Regards from Norway
Terje Kolbeinsen