"You told him something and he got it," he told the Daily Mail.
"I've always very much wanted to be involved in coaching but what distinguished him was self-development. He'd seen so many situations that he knew how to adapt and improvise."
He also found a communicator. "When he started out with us at Everton, he just wasn't good at that," Moyes says.
"But when I arrived at Manchester United, I saw how that had changed. He went out of his way to prove to the outside world how much he had developed in that respect."
The story of Rooney and the six-year-old autograph hunter at United's training ground provides similar insight into the way he is remembered at the club which gave him his best football years, and where he returned with Everton overnight.
The boy was so overawed that he could not be encouraged to join a group of other children who were rapidly accumulating autographs nearby. Rooney, 24 at the time, saw this and approached him. "Could I sign your book, please?' he asked - though the boy, paralysed with fear, could not let it go.
"Would you mind . . . ?" Rooney persisted. The book was eventually passed over. Rooney signed it and then asked: "Can I have my photograph taken with you?"
The episode bears out a collective memory from those inside Old Trafford that Rooney always seemed to know how those on the outside, perhaps lacking his own new-found privileges, might feel.
For all his uncontrollability - which will bring him before Stockport Magistrates on Monday for being three times over the drink-drive limit - it is no exaggeration to say that he is already missed deeply by those within the club.
When the family of Nobby Stiles let it become publicly known that the old man was struggling with Alzheimer's, only one letter came from a United player, past or present, other than Sir Bobby Charlton. It was from Rooney, whose handwritten card said how much he had enjoyed watching footage of him and how sorry he was to hear he was struggling.
When United's Foundation asked the club's players to help them review their Christmas hospital visits a few years ago, they were surprised to find Rooney suggesting a new system which would see more hospitals visited and more substantial presents distributed.
"He was a very active part of that change,' recalls a witness.
When United staff sat down to talk about his testimonial, they were struck by his consciousness that children can be dispossessed and without hope in the place where he had come from: Liverpool's Croxteth. Discussions are currently under way for the creation of a scholarship in Rooney's name, administered by United's Foundation, for a child from a disadvantaged background. Rooney has always wanted to make children's charities a focus. The board of his own trust includes an NSPCC professional.
The same absence of airs and graces always appealed to Ferguson, who first tried to sign him from Everton at 14. It was uncharacteristic of Ferguson that he didn't seem to mind Rooney rolling up for training in slippers.
And it's never been entirely appreciated just how desperate he was not to lose the player when he had publicly claimed United lacked ambition, in October 2010.
The manager was so concerned that he used briefing notes in a pivotal press conference at the height of that saga - the only time anyone can remember him having done so. Every other player who had put himself fundamentally at odds with Ferguson - Roy Keane, David Beckham, Ruud van Nistelrooy - was shown the door. Not Rooney.
It was the lifestyle that disturbed Ferguson infinitely more than the contract disputes, for which he did not condemn Rooney in his autobiography, published four years ago.
Ferguson was an obsessive studier of physiology, who felt that Rooney's broad feet made him susceptible to metatarsal injuries. He also felt that his 'big, solid frame' made an appropriate lifestyle particularly essential.
He knew the problems attached to him drinking much more than the New Zealand Cloudy Bay sauvignon blanc which Rooney's wife Coleen bought plenty of, at one time.
Supporters feel the same. 'Yes, we could live with the contract,' says Darren Jennings, editor of the respected United Pages website.
"It was, '£250,000 a week? OK. But you have to live the life of a top athlete for that'. So in terms of being the player he could have been, it was seven out of 10."
Rooney's drinking has defied rationale, of course. It has not been controllable at times.
Moyes's most vivid memory of Rooney belongs to the days when the prodigy was so powerful that nothing in his lifestyle or on the pitch could possibly impede him. It is his instinctive, 80th-minute goal for Everton against Leeds United at Elland Road in November 2002.
"It was the only goal of the game, at a place where we never seemed to win," Moyes reflects.
"There is this great picture of him celebrating with the supporters. It's the only picture I asked Wayne to sign. I've always kept it."
