Brush?
He probably meant honing, which is necessary to use new brushes. You can use a variety of hone tools: there are ones with little stones mounted in little spring loaded brackets, these will remove a fair bit of metal if misused. Another type has abrasive balls on springy stalks. Another has strips os abrasive cloth, like a "flap wheel".
The idea is to create a rough surface on the cylinder walls. You want a cross-hatch pattern of very light scratches. Then wash the cylinders thoroughly with paint thinner that has a bit of motor oil mixed in. The oil will leave a light film when the final wash solvent evaporates and reduce flash rusting of the iron sleeves. If you wash them with soap and water, you have to immediately dry them with towels and heat and then oil them, or they will turn bright orange with rust in minutes.
The rough surface wears down the edges of the new rings, making them conform to the cylinder wall better and thus seal better. This happens during the first few hours of running, and there are several conflicting views on the best way to "break in" the rings during this time.
