When using sensor lenspen, user is must not rub but in one direction very lightly sweep down using one side, since sensor is not dirty. Only when there is moisture stains, then you have to apply multiple strokes but never rub, follow by final downward sweep to get rid of the dirt. Last step is blower.
Don't buy the big head lenspen as it smudges, use the smaller one instead to remove stubbon stain.