If you are planning on doing an alternating water/dry fast, I have a better method. Do a water fast, but only drink enough water to eliminate mental or physical weakness. Don't drink because of thirst, but push beyond that limit.
Try not to get too dehydrated, though. Dehydration increases the chance of losing consciousness, particularly in hot environments. If you faint, there is no promise that you will awaken. Remember, a slower detox is better than being dead.
In my experience, you will notice the effects of a pure dry fast at least three times as quickly as a pure water fast. For example, people who get weak or nauseous on a 3 day Water Fast will get the same symptoms after 24 hours of a dry fast.