pencil squeezer

Verse of Ian Dury song:

'There ain't half been some clever bastards.
Van Gogh did some eyeball pleasers.
He must have been a pencil squeezer.
He didn't do the Mona Lisa,
That was an Italian geezer'.

Also:

That rubber necked, pencil squeezer Ed Milliband couldn't organize a piss up in a brewery, let alone an effective government ...