You can get an actress doing two different things.
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First you can cast an actress in by clicking on the tent at the porno casting.
You have to adjust the temper you would like to have, which ethnic and how sexy she should be.
The higher your wishes the higher the price. After the casting is done (30 minutes) the results are presented to you (girls in front of the tent -> as far i can remember casting is part of the tutorial).
The results are in general poor (ugly), but sometimes you can get a beauty.
You can hire these girl (max 3 girls at the same time) and they appear under 28 in the filming progress.
They turn into an actress like the girls from the other method.
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Second way is to convince a girl on a date to become fuck buddy (into the red zone and green close the deal button).
If you have been successfull, you can choose her from the fuck buddies BOOK during making an amateur film.
But be carefull some girls don't like the idea of becoming a porn star and leave you forever.
(Try to bang/Do them at first via fuck buddies book and excitement/money. If boys aren't her way, you can use them on films. In general the film way is easier, but some girls react differently:-()
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If you do some films with her, the gauge for actress turns from frosty (blue) to hot (red). At the end she will ask you for a job.
If you got a free slot, you can turn her into an actress by saying yes (lower option) or deny. If you are already maxed out, you can replace a former actress with your new star.