I'd do it directly in Fluent. You want to report the flow time, velocity, volume fraction and mass of the phase. The latter two are to confirm you have enough phase mass to have a meaningful result. You also need to check the flow field: is there something happening to cause a mean value to fluctuate significantly?
The added bonus of the monitors over using CFD Post is the data is retained every time step so you don't need as many data files.