How can a woman verify ritual purity using a cotton swab without invalidating her fasting and prayers?

Dryness from menstruation is one of the two signs of purity, and it is confirmed by inserting something. In this case, the woman is neither fasting nor in a state of ritual purity (wudu') because she is still verifying the cessation of menstruation. However, after purity (taharah), if something descends, she acts upon it and is not required to search and inspect for what has not actually exited. Inserting something during fasting does not invalidate the fast according to the stronger opinion. As for ritual purity (wudu'), it is nullified by inserting something into the vagina and withdrawing it, or by directly touching the private parts with the hand.