Scottish actress Karen Gillan is best known outside Britain for playing the blue-skinned cyborg assassin Nebula.

In two Guardians Of The Galaxy films (2014 and 2017) and the two-part Avengers saga (Infinity War, 2018 and Endgame, 2019), Nebula's martial arts skills are on full display.

During an online press conference for her new movie, the action thriller Gunpowder Milkshake, Gillan admits she was bad at fighting, calling her skills "terrible".

"For the screen test, I remember I had to fight the air to show them I could do it. And it was not good. But the acting part was good enough, so they gave me the role," the 33-year-old says.

The production team for Guardians told her her lack of talent in fighting could be fixed with training.

"They had me in there every single day for training and it was so intense, but I needed it and I was grateful for it," she recalls.

In Britain, she is known for her role of Amy, the companion of the time-travelling title character in Doctor Who (2010 to 2013), a long-running science-fiction television series.

The skills she picked up in the Marvel movies have come in useful in Gunpowder Milkshake, which opens in cinemas today.

Gillan stars as Sam, a hired killer employed by an agency called The Firm. When a job goes awry, she becomes a carer for orphaned eight-year-old Emily (Chloe Coleman).

The movie features a cast of women who have to be as tough as the killers they associate with. They include Sam's mother Scarlet (Lena Headey), who is also a hired gun, and a trio of caretakers of an arsenal for assassins, played by Carla Gugino, Angela Bassett and Michelle Yeoh.

The story centres on Sam and her conflicted feelings about her job and her mother, and steers clear of making her a sex object or giving her a romantic interest.

Gillan says she was surprised by the film's unwavering focus on women as action heroes who fight for friends and family.

"I sort of expected there to be at least something like a romantic interest, and there was nothing like it at all. It feels like this is new territory for a female-fronted film.

"There is a stereotype of female assassins in catsuits and black leather, and when I saw what everyone was wearing, I was like, 'Ah, this is so cool.'"

At a separate online event, American actress Gugino, 49, talked about her character Madeleine, an enigmatic and fastidious keeper of a secret arsenal who must take up arms against a group of thugs.

Gugino's career includes roles in action-comedy franchise Spy Kids (2001 to 2011) and crime thriller Sin City (2005), as well as the title role in the crime-thriller series Jett (2019).

As befits a weapons expert, Madeleine's chosen tools are unique. They include a tomahawk and a large, electrically operated machine gun known as the Minigun, a weapon that can unleash a hailstorm of bullets and is as long as her body.

Gugino could operate the gun easily, but she had to first hoist it into firing position. The problem was, it was stowed inside a van. To get it ready for aiming and firing, she had to lift it above her head, through an opening in the van's roof.

"I tried to lift that thing and it was so heavy. I was like, 'We have to get a guy in here to help'," she recalls.

With training, however, she found she could do it by herself, while clad in dress shoes and sensible office wear.

"So I can say I lifted my own Minigun. But it was no joke," she says.

• Gunpowder Milkshake opens in cinemas today.