The Ibrox outfit announced on Sunday that former manager Smith and retired businessman Ian Hart had joined the board as non-executive directors.
McCoist told the club's website: "The one thing you can guarantee is that Walter will ensure that decisions are being made in terms of the best interests of the football club and the supporters.
"It's a clever move by Charles Green to get someone of Walter's stature on the board.
"I'm really pleased that Walter is back. I am in regular contact with him and I'm lucky enough to count on him as a very good friend.
"It's a great move for the club, a tremendous move for the supporters and
hopefully it will prove to be a very good move for Walter.
"He was eager to make the point that he won't be standing on my toes. We had a good couple of conversations and he wanted to make it crystal clear to everyone.
"It's a brilliant thing for me because he is great contact between me and the