First there is no way to remove pitting except to remove the metal down far enough to get to the bottom of the pits. And if the pits are deep enough to be visible, that means removing so much metal the barrel would be ruined. I don't know of any magic cleaner that will really get all the dirt and crud out of pitting without a lot of work. It is like one of those street sweepers trying to get all the dirt out of potholes.
Over the years, powder fouling, primer residue, metal scrapings, general crud, and the remains of old cleaners have gotten into that pitting and getting it out is not easy. In fact, many shooters eventually decide to just let it be and try not to add too much to it.
Abrasives may make the unpitted area shiny and the barrel may look better, but they still won't get the crud out of the pits or eliminate them.
Jim