Welcome to Curezone. Some people go straight into the Liver Flush the last day of their MC.
You may be able to get magnesium citrate at a drugstore. It would be in the laxative section. If not, call around to your local health food stores and see if they carry it.
Most people on the forums use Dr. Hulda Clark 's recipe for liver flushing. Click on the link below and you can find this and also lots of good information on liver flushing.