How did the director get actual Mennonites to cooperate?

I'm actually Mennonite, and I've met Mennonites from a variety of different areas and backgrounds: Russian-German Mennos from Manitoba, Ontario, Alberta, BC, Saskatchewan, Paraguay, and Mexico; Swiss-German Mennos from Pennsylvania, Southern Ontario, Ohio, Delaware, Indiana, Virgina, the Carolinas, and Texas; and non-white Mennos from all kinds of ethnic backgrounds and nationalities (including the president of the Mennonite World Conference, who is from Zimbabwe).
We Mennonites can be a very diverse and complex group. There are some groups that maintain the very traditional way of life, while others look exactly like their neighbours in the most liberal, grungy, inner-city setting you can find. My extended family grew up on farms in Pennsylvania, wearing traditional clothes like plain dresses and head coverings, staying out of politics and the military, and limiting exposure to the world of media (they had books, radio, and records, but no TV). But the Mennos I go to school with have grandparents and parents who grew up in a very liberal, modernized setting, distinguished from their urban neighbours only by their deep faith and pacifist worldview (and maybe love of music and Russian Mennonite food like vereneke).
I know some Mennos who supported Bush and the war, and others who hated Bush and hate war. I know some who believe in simplicity, buying as little as possible and not putting faith in consumerism, while other Mennos have huge houses, cars, and all the latest technological gadgets. My conservative Menno friends in Pennsylvania were very plain (traditional and isolationist), more like Amish than anything else. But some of my cousins wear flashy jewellry, drive nice cars, or work in far away places among atheists and Muslims.
There are some common elements between the different groups, but even these can be blurry. Pacifism, simplicity, and adult baptism are the traditional cores of the faith, which many Mennos still hold, but some people who consider themselves Mennonite (as an ethnicity or cultural heritage) do not even believe in God. What we share most often is a common history, but even then you have two branches of Mennos, one from Northern Germany/Netherlands/Russia, and another from Switzerland/Southern Germany, and we can be quite different from each other. For example, the first group used Low German as their traditional language, and many still speak it, while the second group used "Pennsylvania Dutch," an Americanized low German that is quickly going out of use.
A lot of Mennos love the arts, and would gladly go into acting or film-making. Although I can see why you would be confused about the Mennos in this movie. The Mexican Mennos are usually Old Colony Mennonites, from the German/Russian background, and tend to be rather traditional and isolationist. But while they believe in simple dress and quiet spirituality, they have adapted modern technologies and other benefits of Western wealth.
By the way, Miriam Toewes, who plays Esther, is from Steinbach, Manitoba, 45 minutes away from my school here in Winnipeg (Russian Mennonite central). She's an author, and she puts a lot of her experiences growing up in a conservative Menno community into her books, such as "A Complicated Kindness." Her family was politically conservative, and didn't believe in drinking or dancing. But they seemed to dress modernly, and have rather modern lifestyles in terms of schooling and economic livelihoods. Toewes felt very restricted by her Menno community, and left to wander at an early age. But eventually, she came back to the area, and is now living as a secularized Menno in Winnipeg.