The ಶನಿ vrat is kept on ಶನಿವಾರ — traditionally one meal after sunset, without salt. It is the household remedy for a weak ಶನಿ, and unlike a gemstone it cannot be kept against your chart.
The weekday fast is the household remedy — kept on the graha’s own day, usually one meal after sunset and no salt. It is as much a discipline as a ritual: the point is the weekly act of restraint, held long enough to mean something.
The Saturday fast abstains from grains and oil-based foods, and is usually kept alongside service to elders and labourers.
A difficult Saturn reads as delay, isolation, chronic strain and a sense that effort does not convert. Saturday service to elders and labourers, and Hanuman worship, are the classical response.
ಶನಿವಾರ. Fasting, charity and mantra japa for ಶನಿ all belong to that day.
The mantra, the weekday fast and the charity are safe for anyone — they address ಶನಿ without amplifying it. ನೀಲಮ is not: a planetary gem strengthens whatever the graha is already doing, so it needs a chart reading first.