The PM9 slide and barrel are SS. Unless you have a problem looking for a solution, I would not do anything to it until 500 rounds have been through the gun.
It will self polish where it needs to by simply suffering through the first 500 rounds, then it becomes amazingly better. Leave it alone, is my advice. The revolver style DA trigger pull is amazingly smooth, and better than most revolvers, but takes some getting used to.
The gun is not a smooth action piece, when cycling by hand, but shoots fine. There is a square cut edge at the top of the barrel chamber that must ride under the slide on action. It may bother you but it works fine, even if you leave it alone.