I've had some success using this technique, mainly because my fly casting is so bad I usually just stick the bubble on. I rig it as follows. Attach to main-line;attach leader of at least six feet length, use two flies, one on point and a dropper. The other method is to have the bubble at the end of the cast, with your flies coming off droppers above the bubble.This method can often be better if the takes are cautious or hesitant as it allows for better registration of shy bites. Also, play around with the depth you want to fish. For deeper lying fish fill the bubble, for surface/sub-surface only fill one quarter of the bubble. Also, use the smallest bubble you can get away with. The great thing about this method is that it lets you really search a river. Don't be afraid to work this method, rather than just casting & retrieving.