Be careful! The receiver is anodized alluminum alloy. IMHO, the best way to smooth a Mossberg action is to shoot it. You would be amazed and what 50 rounds can do.
To field strip.... With the gun UNLOADED and the hammer cocked, push out the pin that holds the trigger group in place. Pull up and forward on the trigger guard and remove the trigger group. Remove the shell stops. If you shake the gun they will probably fall out. Move the slide back until the bolt carrier lines up with the cutout in the receiver. Lift it out. Move the slide forward and push the bolt out the front of the receiver. Squeeze the arms of the shell lifter together and remove. That's it.
If you have a problem understanding any of this while looking at your shotgun, don't do anything. Leave it alone!!!