Use only a very small amount of fluid on the sensor swab—typically about 2–4 drops. Based on the community answers, the attached stick/cap is generally not something you remove and use separately; the goal is simply to transfer a tiny amount of fluid to the swab. Some users report wetting the swab corner directly from the open vial by lightly touching or dipping the swab tip, then repeating on the other side if needed. Others describe letting a few drops from the attached piece fall onto the swab. In either case, the important point is not to oversaturate the swab. Too much fluid can leave streaks or create more problems than it solves. Follow the kit’s instructions if available, and apply the fluid to the swab—not directly to the sensor.