I just finished a 12 day Master Cleanse and did a SWF (Salt-Water-Flush) every morning. Here are my recommendations:
Mix exact proportions of Sea Salt & water and take on an empty stomach. Do no drink additional water for at least 1 hour after drinking the SWF.
Lay on your right side after downing the mixture to aid the stomach in dumping it out
For your first time give yourself at least 2.5 hours at home by the potty
On the Master-Cleanse forum, we call it 'butt pee' and it is just like it sounds...