The Triggger Wash requires the use of water with it. You are meant to spray the car down with water, spray the Trigger Wash, use a wash mitt, then rinse. Basically the Trigger Wash is meant to replace making up a bucket of shampoo. You also need to rinse off the mitt frequently, as you have no bucket to dip it into.
The S+W is a waterless wash, so you can use it even when stranded on the highway waiting for a towtruck.