Spinning prop with plugs out.

Just changed the oil on my rotax 912. Normally after an oil change I burp the system, check the level and then continue on with operation. After reading a Rotax maintenance document I decided to try to see if I could get an oil pressure reading by turning on the master switch and having someone watch the pressure gauge while I spin the prop. 
Here's my questions: I removed all of the plugs on accident, instead of just one from each cylinder. Is it possible I could have created hydraulic lock from spinning it without any plugs in? I haven't started it yet, so as long as I burp it with the plugs in before starting it should I be okay? 

Also, what kind of oil pressure should I be getting if I do the test correctly with one plug out of each cylinder. And is this a recommended practice?