The undying mythology of the American West forms the premise of HBO’s popular show Westworld—that the wealthy of the future would pay to vacation in a massive virtual Old West theme park. And indeed, cowboys embody a certain pure spirit and romanticized version of American history that people around the world identify with, even if only by wearing a pair of boots or a Western shirt.

This may explain why in parts of the US and Canada, the so-called “cowboy church” movement is spreading—”like a wildfire,” according to one follower interviewed by Texas Monthly in 2014.

A couple of decades ago, only a handful of these churches existed. Now, says Greg Horn, a self-described cowboy who works for the Texas-based American Federation of Cowboy Churches (AFCC), his group alone includes more than 200 “partner” churches. There are other smaller associations, and hundreds of independent cowboy churches affiliated with various denominations, says Horn. His guess at the total number of cowboy churches: “You’d be low at 500.”

A cowboy church is exactly what it sounds like: a church made for cowboys. The services include country music and visual props of cowboy culture, such as tents and rustic fences. Baptisms might be held in a stock tank, the metal tubs that normally hold drinking water for ranch animals. Cookouts and trail rides replace coffee and donuts.

Cowboys, the federation warns its member churches, might be turned off by public displays of emotion (especially the hands-in-the-air exuberance of evangelical churches), and they dislike long sermons, so pastors are advised to restrict themselves to 20 minutes and avoid churchy words.

Courtesy the American Federation of Cowboy Churches More elaborate than coffee and donuts.

These aesthetic choices may not be for everyone, but the rapid growth of the cowboy church movement is based upon a set of principles that make a lot of sense—and they offer lessons for other organizations and grassroots movements.

The key to the strategy is recognizing that not everyone who attends a cowboy church has to be a real cowboy (just as not everyone who wears a Canada Goose jacket is an Antarctic explorer). There aren’t many authentic cowboys left, and certainly not enough to fill the pews at the hundreds of organizations that call themselves cowboy churches in the Western US states and Alberta, Canada. That’s why the AFCC’s “Bull’s Eye approach” comes into play.

To begin, the AFCC says, a cowboy church should know who it must win over: Real cowboys, as in professional ranch hands or wranglers, who work on horseback. These cowboys are often “lost and unchurched,” according to the AFCC’s training documents. To make them comfortable, the federation suggests avoiding “fancy brick buildings, stained glass, steeples, red carpet, plush pews” and “fancy clothes.” Such accoutrements, it observes, “say to the lost in the cowboy culture, ‘You must clean up and get right first before you come to church.'”

Cowboy churches should avoid that alienating message, the Bull’s Eye approach dictates, because the cowboys—”lost” as they may be—represent the red dot, the target, who build the brand’s credibility and thereby passively draw in the wider, more populous circles around them. “The more cowboy you make it, the more people will flock to it,” says the AFCC.

The next circle is “arena cowboys and cowgirls” (professionals on the rodeo circuit, for instance); followed by “horse people,” “cattle people,” “cowboys at heart,” and finally the “cowboy mentality people,” in the broadest category that makes up the outer circle.

The “cowboy mentality people” might not even wear the boots or have a horse, Horn tells Quartz, but “you’re going to have a thousand of them or more for every working cowboy, demographically.”

It may seem counterintuitive to focus on the few instead of the many, but the idea is consistent with general marketing theory: Not every Whole Foods customer needs to be a health nut, and not everyone who shops at Patagonia must climb mountains, but both are brands whose broader identity is tied to a targeted customer type. Each “let their customer base (and their businesses) grow organically from a core base of early adapters to more mainstream consumers,” writes Inc. magazine columnist Debra Kaye. They are now, of course, among the biggest brands in the country.

For Horn, the Bull’s Eye approach is not a marketing tool, but rather a spiritual calling, he says: “The wisdom of man would tell you to focus on the 1,000, and the most prestigious group—but the Bible says the wisdom of man is foolish.”

Here is the full text of the AFCC’s advice to burgeoning cowboy churches: