Rahu daan is given on Saturday: blankets, black sesame seeds, black gram (urad dal), mustard oil. Charity addresses a graha without amplifying it, which is why it is prescribed where a gemstone is withheld.
Daan is charity aimed at a specific graha, given on its day and matched to its significations. Classically it is the remedy that works when a gemstone would be dangerous — it addresses the planet without amplifying it, which is why it is prescribed for Rahu and Saturn where stones are withheld.
Rahu charity is blankets, sesame and mustard oil, given to the homeless and to those struggling with addiction or mental illness.
An afflicted Rahu shows as anxiety, addiction, scandal and chasing what recedes as you approach it. Durga and Bhairava worship, and eclipse-day practice, are the classical response.
Saturday. Fasting, charity and mantra japa for Rahu all belong to that day.
The mantra, the weekday fast and the charity are safe for anyone — they address Rahu without amplifying it. Hessonite Garnet is not: a planetary gem strengthens whatever the graha is already doing, so it needs a chart reading first.