I think Cinna got a job working as a stylist so he could help tributes like Katniss in any way he could, and rebel in his own silent way. Cinna isn't the same as everyone else from the Capitol, and he understands this.
I haven't watched a lot of movies recently, but I couldn't miss this one. I read the books(which were amazing btw.) and the movie is just breath-taking and I can proudly say that, this movie is as good as the book ! Love it !