Rottenstone and oil on a felt pad (or wad of felt) and elbow grease.

When you do it avoid the temptation to do it in small areas. Make your strokes long and overlapping. It will take longer to see progress but you will not need to spend the rest of your life trying to blend the areas together.

Mark Begich, Joaquin Jackson, and Heller resistance... Three huge reasons to worry about the NRA.