I used to scrape it off the garment of the Messenger of Allah ﷺ. So if you see it, wash it, and if not, just sprinkle water over it.
حدثنا محمد بن أبي عدي عن سعيد عن أبي معشر عن النخعي عن الأسود
كنت أفركه من ثوب رسول الله ﷺ فإذا رأيته فاغسله وإلا فرشه
Its isnad is sahih. Muhammad bin Abu Adi is attributed to his grandfather, and he is Muhammad bin Ibrahim bin Abu Adi, who is trustworthy according to Muslim and the Sunan compilers. Saeed is Ibn Abu Aruba. Nakhai is Ibrahim bin Yazid. Aswad is also Ibn Yazid. They are all trustworthy, and their hadiths appear in the collections of the group. Abu Mashar is Ziyad bin Kulayb, who is trustworthy, and his hadith appears in Muslim and the Sunan compilers.The hadith was narrated by Muslim, 1/228, number 288, Abu Dawud, 1/101, number 371, Tirmidhi, 1/198, number 116, who said, hasan sahih, Nasai, 1/156, number 330, and Ibn Majah, 1/179, number 539, all of them in the chapter on purification.