Thompson, who worked with McCartney for the duration of his 11-year term as senior coach of Geelong and then the past season as assistants at Essendon, said the new coach of the Western Bulldogs had helped him develop as a person.
Thompson has also revealed McCartney was the first assistant he hired after arriving at Geelong for the 2000 season after hearing great things about his coaching ability.
""I went for the Richmond job and Jim Malone, the [former] general manager said 'if you take the Richmond job, you probably won't know this guy but he's an excellent coach and from all the guys at Richmond, he'd the one guy I'd keep',"" Thompson told SEN on Tuesday.
""Then Danny [Frawley] got the job, Brendan left, and I knew he was a Geelong boy and we interviewed him and within two minutes, I said, 'You've got a job here, buddy, you'll be fantastic for us'.
""He's been a tremendous coach for all the time I've met him and we've sort of helped each other become who we are today.
""I'm very, very happy for him and I think it's well deserved.""
McCartney has not played the game at the highest level, having run out for Geelong club Newtown for 87 games before coaching Ocean Grove to four consecutive premierships in 1994-97.
Thompson said it didn't matter his former colleague didn't have the experience of playing AFL himself, and it was instead a ""great thing for the industry"" that clubs were looking beyond playing records.
""The NFL went through a long period of 'coaching coaches' who didn't play football, they had a career in coaching and they turned out to be great coaches,"" he said.
""I don't think, if you've played the game at the highest level, that it necessarily means you've got an advantage being a coach.
""I suppose what people who haven't coached have to do is prove that they can coach, and he has done that.""
Thompson described himself, McCartney and new Adelaide coach Brenton Sanderson as ""the three musketeers"" who were clones of each other.
He also praised the Bulldogs for taking a punt on an untried coach, and said the players had plenty to look forward to.
""It's a good story. I would have thought the Bulldogs may have gone for the easy choice but I think the board have made a really good decision based on skills, sense and personality, and how they can take their club forward,"" he said.
""Some boards just don't take that risk because of the fall back later on.
""If you were a player at the Western Bulldogs and you heard his press conference [on Monday], you'd be pretty impressed straight away.
""That's the impression most people get when they meet the man.
""He just knows his caper, he's got a huge desire to work and help and develop people, and you can't help but be impressed by him.""
