This short fishing video shows how to rig your leader with two dry flies on the same line. Using a Blood Knot Dropper for this set up is the best way I have found to keep your dry flies floating and acting naturally. Consider placing the largest dry fly at the end of the line and the smaller off the dropper knot.
Fishing from the boat with double dries is my favorite way to catch trout. If you would like to pitch dry flies at the bank and watch trout after trout come up and eat them, the Roaring Fork River in Colorado is the place to be. Go to http://www.riplips.com for information and booking.