Load your rotating floor buffer with its heavy refinishing screen. Start the buffer. Push it forward and back over the floor in the direction of the floorboards, taking off the top coat of gloss.
Vacuum up the dust.
Screen the floor in the same manner two more times, with the medium and fine refinishing screens, getting the surface smooth and bare. Vacuum well.
Spread polyurethane onto the floor with a paintbrush, applying it in a thin coat along the length of the boards. Start at the far corner of the room and work your out toward the door.
Allow the polyurethane to set for six to eight hours. Sand it by hand with extra-fine sandpaper, enough to dull the shine. Vacuum up the dust.
Apply a second coat of polyurethane gloss onto the floor. Let it dry, sand it by hand and vacuum.
Apply a third coat of polyurethane in the same manner. Let it set for 24 hours before walking on the floor.