MP will increase as RPM decreases (propeller control move back), if the throttle is not touched. The MP has a relationship to the torque required to turn the propeller, if you coarse the blades, the torque goes up.
Cycling the prop during the run up, or while taxiing out, just assures that warm oil is in the propeller hub, and the governor will be able to coarse the blades, and thus prevent an overspeed at the point of takeoff. If you cycle the prop, and the RPM reduces, MP increases, and you hear a "whoosh", you're all set...
I would not fixate on the oil pressure indication, you might not see a change with prop motion. As long as the prop works, you're all set. Assure oil pressure is adequate for engine operation before take off - for the engine's sake.