[EnigmaticSingularity]

hmm, have a lunch bag in the backpack with a battery powered fan rigged to the top of the lunch bag and have two or 3 water bottles resting outside of the lunch bag with plastic hoses coming out of them and then use something similar to whats used in a spray bottle to spray water at the dry ice whenever you need smoke. instead of a trigger to make the water spray you should be able to rig up an air pump to compress the spring to spray water. I apologize if i don't make sense i can't really put into words what i'm picturing in my head.