The film, which stars Compston as a younger Ferris, tells the story of how he entered the city's crime underworld, working his way up the ranks as an associate of Arthur "The Godfather" Thompson Sr.
Compston, who found fame in Ken Loach’s Sweet Sixteen, discusses what it was like to play such a notorious figure, how he shaped the character and his experience of meeting Ferris in real life.
Ms McMonagle, known for her work on River City and Lip Service, plays Ferris’s girlfriend Anne-Marie.
They also talk about the disappointment in failing to secure permission to film in Glasgow, instead having to shoot scenes in London.
The Wee Man is in cinemas from Friday 18 January