During those classes, which took place between 2010 and 2013, he allegedly kissed the women and touched their breasts and genitalia.
The man denies the charges and his lawyer, Ron Mansfield, says his client used legitimate acting exercises and the touching never happened.
The four complainants conspired after he ended an extra-marital affair with one of them, Mansfield said.
One of the complainants, none of whom can be named, started giving evidence this morning.
The former model told the court she joined the agency in 2011 after being scouted in Takapuna. She was signed up to acting classes to help her progress.
After her first camera awareness class, the woman told the court the acting coach approached her and said she had great potential and invited her to attend his group classes.
The classes involved men and women in their 20s and 30s.
During those classes, the group would do an exercise called "push/pull" to music, she said.
"The objective was to switch off, to put all your focus on them and to see what would happen."
She said she admired the acting coach because he created such a supportive environment and encouraged everyone to step outside their comfort zones.
"I really looked up to him."
Six months after her first session, he approached the university student, then in her early 20s, after class and told her he saw something "really special" in her and wanted to be part of her journey as an actor.
The one-on-one sessions, held in his office with the door locked, started with one every two or three weeks and cost $60.
After a few months, the hour-long classes became more frequent - up to twice a week and the price dropped to $30 each.
During the sessions they would do 10-15 minute push/pull exercises, but this time they felt more intimate, she said.
She said she followed his lead when they tapped each other on the shoulders and head before sitting down and discussing the exercise.
"The first time, I felt clumsy and awkward and I didn't know what I should to do."
He told her she was one of the best people he'd ever seen doing it for the first time.
"I walked out of there thinking I didn't do too badly, that's really cool - I was one of the stronger people."
As the classes progressed, the acting coach got closer to her. At one point he brought his cheek very close to hers and "just hovered there".
She responded with a tap.
At another session, he kissed her on the cheek, which she said made her feel "very uncomfortable".
She responded with a tap on his shoulder then he kissed her on her other cheek and she thought "Oh my gosh, it's my turn now" so she kissed him on his cheek.
He told her afterwards: "You did really well. You're really getting it. You've just got to let go."
He also told her she was sexually inhibited.
Eventually, the kissing progressed to "a pash" and he grabbed her face with his hands.
Although she never told him it made her uncomfortable, she said it was "very obvious" from her reactions.
When she kissed him back, the woman said he was "very happy" at her progress and skipped around the room.
She said she always "felt bad" if she didn't match him and he made her feel guilty about "missed opportunities".
He would allegedly tell her: "I'm doing this for you. I'm helping you open these boxes. I'm helping you overcome these inhibitions."
She said: "I was trying a new hobby I was trying something new with this acting thing and because I was paying for it I wanted to see where I could take it."
He just tried to touch more and more after that point.
At one point, they moved into a smaller room with no windows. She lay on the floor and he allegedly pulled down her jeans then performed oral sex on her for a few seconds before she stopped him.
She told the court she burst into tears because she was "confused and mortified". He told her "it's okay, I'm scared too", she said.
"What was right and what was wrong had been blurred and I wasn't sure of anything any more."
She said it made her feel nervous.
"I didn't want to let him down any more. I was trying to be brave."
Crown prosecutor Claire Paterson alleges the man indecently assaulted four women and twice sexually violated the woman who is giving evidence today by "pleading" with her to kiss his penis.
But Mansfield said the evidence would be "hotly contested" and his client denied touching the women's breasts and genitalia.
He said the complaints had been exaggerated because the women felt slighted.
The women will continue to give evidence this afternoon.
The trial is expected to take two weeks.
