A pathetic or defensive measure nerds with social problems take to avoid being thrown out of a convention for being a creeper. Due to their lack of experience with women and an outright paranoia of security throwing him out. The Hover Hand Technique is like a photo version of a thigh job. You are less likely to get thrown out of a con that way than if you actually held on to the girl and the girl cries sexual harassment.
Joe was at an anime convention with his friend Dan, while Dan was an atypical nerd with relatively good looks, Joe was anything but charming and had concerns about taking photos with a cute maid cosplay. While Dan went straight in for the kill with one photo having him grab the girl by her hip and later made a kissing face on her cheek. Joe was happy to hover hand over the same girl.
Dan wasn't so lucky when the manager of the maid group threw his ass out of the con. Dan went off to get drinks at the bar where he can be at home with his kind of people whereas Joe remain in the con.