jackoff artist
A person (usually a man) who is good at masturbation, but since that rudimentary skill requires no particular training, it's usually used to mean someone who has no particular skills at anything beyond masturbation. An American way to designate a "wanker."
"Bob says he's an air-guitar artist."
"Bob is a jackoff artist at best. I'm not even sure he can perform air-guitar."
"Bob is a jackoff artist at best. I'm not even sure he can perform air-guitar."