ok i have tried the shaving cream thing and it works.
1. you take shaving cream and stick it in the freezer
2. after like 12 hours or so take it out and get it to your target as fast as possible.
3. poke holes and stuff in the container and put it wherever you like (the car is a great place, between the glass door and their front door is another because they open the door their house will have oodles of SC in it.)
the shaving cream thaws and expands and get EVERYWHERE. so if you put like five or six in someones car it will FILL the car with cream and it is very cool. definitly try this.