How to Fix Swirls on a Wooden Floor

Load your drum sander with rough sandpaper. Run it over the surface of the floor, with the direction of the boards, working across the whole floor. The sanding should take off most of the old finish.

Vacuum up the dust.

Re-load the sander with its medium sandpaper belt. Re-sand the floor, with the direction of the boards. It should remove the old finish and leave the wood bare. Re-sand the swirl marks as needed until they are gone. Vacuum up the dust.

Sand the floor a third time, with the fine sanding belt, getting the surface flat and clean. Vacuum well.

Brush wood stain onto the floor with a paintbrush, working in sections, a few square feet at a time. Brush it on heavily enough that it puddles. Let it sit for one minute. Wipe up the excess stain with rags. Repeat for each section, doing the whole floor.

Let the stain dry for 24 hours.

Brush on polyurethane onto the surface in a thin, even coat, applying it with the direction of the floorboards. Begin at the the far point of the floor from the entrance, so you can work your way out of the room.

Let the polyurethane dry for six hours. Dull the polyurethane with extra fine sandpaper, by hand, with quick, light strokes.

Apply a second layer of polyurethane. Let it set for six hours. De-gloss it with extra-fine sandpaper. Apply a third polyurethane coat. Let it set for 24 hours.