I read in the instructions that you can have a laxative tea first thing in the morning and again in the evening. The SWF (Salt-Water-Flush) is not a must, but it's recommended if the laxative tea doesn't work. Hope this helps.
If you want more info, go on to http://www.frenzy.com/~sam/mc/TheMasterCleanse.pdf#search='master%20cleanse%20fast', you'll get the whole book in .pdf format (this means you'll need Acrobat reader to view it).