I recall once hearing that Money for Nothing was a cocked wah into a Marshall, with an SM-57 pointed straight downward about six inches above the floor. But lots of people have different stories about that tone. Kinda like Spirit in the Sky; some stuff happened and it ended up creating a totally unique tone, and then they said "huh" and moved on from it, leaving the rest of the world to try and work backwards to figure out how the hell they got there.