Is looking at the garment sufficient to check for light istihadah (yellow or brownish discharge), or is it necessary to insert cotton into the vagina?

A woman with prolonged non-menstrual bleeding (istihada) and a person with urinary incontinence ( سلس البول) must perform ablution (wudu) for each prayer if anything exits. If nothing exits, they are not required to repeat the ablution. She is not obligated to insert cotton into her vagina to check for istihada, because the exit of secretions from inside the vagina to the outside invalidates ablution. What is meant by "outside" is what becomes visible when she sits on her heels. It is sufficient to pass a piece of cotton over this area; if there is any yellow or brownish discharge on it, she must perform ablution, otherwise, her purity remains.