If you don’t know whether or not it’s fully cured, consider waiting 30 to 60 days. If the surface is cool to the touch, it’s not dry. If you sand it lightly and get a fine powder, it is dry and ready to go. [2] X Research source
Not all paint thinners are suitable for oil-based polyurethane finishes. Make sure that you use the right kind.
If you diluted one of your cans of polyurethane, then you should apply the diluted one now.
After the final coat, use a piece of cardboard to buff the surface and make it especially smooth. A high-gloss finish is not necessary or recommended for floors.
