Finishes that dry before they level out can show the texture of whatever tool was used to apply them. Overly fast drying happens most often with waterborne finishes, and is exacerbated by too much air movement, working in excessively hot conditions, or the finish drying in direct sun. Other causes include not applying enough finish, applying it unevenly, or not keeping a wet edge. An applicator with hardened spots can leave marks. Flattening agents in satin or semi-gloss finishes can remain at the bottom of the can if not properly stirred, which can accentuate applicator marks. Stopping and starting the applicator in the middle of the floor also allows flattening agents to settle out and leave a mark.
Screen and recoat after the finish has dried sufficiently. Sometimes a complete re-sanding to bare wood is necessary. The difficulty will be getting the floor flat. Any ridges left after screening will telegraph through the fresh finish. To check for flat, run a wet towel across the sanded floor and look across it toward the light, which will highlight any remaining ridges. The more rigid the sanding screen backer, the flatter the floor will become. Darker colored pads are generally stiffer than white pads. Whereas a white pad will flex over the ridges, dark pads keep the screen flatter, cutting off only the tops of the ridges and leveling the floor faster.