A: You have applied the stain and 1 coat of polyurethane. One coat is not enough. You will get greater penetration in some boards and areas than others, since the density/hardness of the wood is not equal and consistent from one board to the next. When I do a job, I usually use a polisher with a 180 grit screen for the main area, but rub the edges with 120 grit to assure adhesion and smooth off any rough spots. So, if you are going to rub down all the floor area by hand, 120 grit should be fine. Just be careful not to rub so aggressively that you cut through the finish and remove the stain. Vacuum the floor and wipe it down with a well rung out water dampened cloth and apply the next coat. Any succeeding coats will follow the same process.

