The Guinea-Bissau-born forward, 22, signed from Vitoria Guimaraes on a four-year contract in the summer, but has spent most of his time on the bench. During pre-match warm-ups and at the interval he can be seen being put through his paces by McGrain.
"Big Amido is only a young man and he wants to be better," said former Scotland and Celtic full-back McGrain.
"I give him some exercises with the ball. I enjoy doing it, rather than standing about seeing the other boys working with the sports science people.
"He enjoys doing it, he enjoys kicking the ball and heading the ball. He hasn't had many games but he is getting better.
"He came here with a good record of scoring goals. He scored against Liverpool in pre-season and against Kilmarnock.
"That is his job, to score goals, and if he does that we will all be happy."
The coach was speaking yesterday at the launch of The Quality Street Gang - a book about the talented Celtic reserve side of the late 1960s and early 1970s, which included stars such as Kenny Dalglish, Lou Macari, David Hay, Paul Wilson and McGrain himself.
McGrain said they learned their trade with the help of the Lisbon Lions, the Hoops team that won the European Cup in 1967.