Wait till they're asleep, leave puddles and hope something steps in it, spray it as a mist from a discrete location, etc. Spray would be much more discrete than latching onto something's face for 24 hours. The amnesia is only useful if the thing is alone when and while you hug it.
And if you're gluing people to walls in hives, they know they're f**ked because they wake up glued to a wall -- so why bother with the hugging process then?