You want to do the Liver Flush when you are back on solid foods. So about a week after you end the MC. You probably want to plan being around a bathroom for one day when you do the liver flush, so if you begin Friday night, you might want to stay home Saturday.
If you want to prevent nausea, add a tsp of turmeric and a tsp of ground ginger to your olive oil/grapefruit mixture and then blend it in a blender.