poison gas? hose him down with cyanide and chloroform...or use 100,000,000 gallons of that foam or gel/gunk that cops will use for riot control in the future. it was in the episode of the simpsons with the female robot cop....
if the hulk is covered in that, there is nuthin he can do since he can't get any leverage or jump...KINDA like fightin ur way out of quicksand...he'll be in the center of a foam ball