Pour some petrol into a container.
Get some polystyrene and put it in the petrol, until the petrol won't dissolve anymore. You should end up with a sticky syrup.
Apply to the door, the walls, the subject and his customers.
Requires a naked flame to harden
Edited to add, this is just a hypothetical suggestion. If you are silly enough to make this at home and attempt to harden with naked flame, you may end up doing an impression of a toasted Vietnamise girl running from a flaming village.
If you DO try it, please get a friend to video it and post the results here.
Do all of the above with fucking up his door, then put a big plank of wood and nail/glue it over his door and put police tape over it. It will then look like his door has been kicked in by the police. Also see if you can get a rotton fish stuck half way in the netter box?
No water required; assuming the doors are closed it will fill the average flat hallway up to about kneeheight with foam which will set tacky in about 1 hour and hard in 2-3 hours. If you go for this, don't get any on you as it sticks like shit to a blanket. The end result is pretty much identical to squirty aerosol foam, but much cheaper.
Fucking gutted! hear some noise outside the flat nonight and had a quick look out the window the plod showed up and kicked his door in. Bugger mind you looking forards to printing some BFO posters for the doors saying junkies this is now a dealer free zone....fuck off