I've had Beretta and Browning O/U's. The Berettas were by far the stiffest out of the box, to the point of having to break them open over your knee. The "removing lubricants" route made it even worse, so I chose to lubricate moderately and shoot the guns. I shoot of lot of skeet and sporting clays so it went fairly quickly, but it took over 1,000 rounds for the Berettas to start feeling "smooth".
The Brownings came with much heavier "grease" so I cleaned and re-lubed them with my usual gun grease/oils. Even after multiple thousand rounds, they still feel stiffer than the worn-in Berettas, though not to the uncomfortable/hard to open or close.
As previously stated, It appears that the Italians like to start with a stiff gun and let it wear in. My Berettas have 10's of thousands of rounds through them and they fall open, but lock up tightly. Better with age seems to be the rule.