Phelan, who played under Ferguson at United, is still involved in talks over a permanent deal despite the Tigers' impressive start to the season which won him Manager of the Month award for August.
"We have a coffee when he's around. We have a chat on the phone, but he's a busy man. He's a bit busier than me," he said of Ferguson who also assisted at Old Trafford.
"He's always in the background and I would never not want to be in his company, because he's a fascinating guy.
"Everybody in football, and football people, they want you to be successful and do as well as you can.
"When that opportunity comes you can always rely on people who send you good luck messages when you're ready to perform, well dones when you've done well, and also a little bit of advice when you haven't."