The two key considerations in choosing a wood-floor finish are resistance to scratches and the large surface to be covered.
To stand up to abuse, you need a very durable finish, and to avoid filling the room with overspray that will settle and stick to the finish, you need one that dries slowly enough so it can be applied by hand. The two best choices are oil-based polyurethane and water-based polyurethane.
Oil-based polyurethane is more durable than water-based, but it has a strong odor that hangs around for several days, and it has a slight orange coloring (usually referred to as “yellowing”). Water-based polyurethane has very little odor, almost no coloring, and it’s much easier to clean up. Water-based polyurethane also dries relatively rapidly. So you have to work much faster, being sure to keep a “wet edge” so overlaps don’t show.
Oil-based polyurethane is the best choice if the color and odor aren’t problems. Water-based polyurethane is the best choice if you want to preserve the color of a pickled or very light wood, or if odor is a problem. You may be able to buy a more durable, two-part, water-based polyurethane from a flooring-supply store. Be sure to check on the toxicity of the product and the safety precautions you should take.
Use a large brush, sponge mop or lamb’s wool pad to apply oil-based polyurethane. Use a large brush or paint pad to apply water-based polyurethane. A paint tray provides a convenient reservoir to hold the material.