As others have stated before me, JB doesn't have to go out to find those guys, they find him.
It's well known that Joshs' marriage was pushed hard for by his parents, and the reason for that became obvious when it was revealed that he was a horny teen that couldn't keep his hands to himself, even when his hands were wandering over his own sisters and the daughter of a family friend. Even after being 'disiplined' once, he kept groping his sisters, culimating with the molestation of his five year old sister. Getting him married off quick so he'd have a "godly" output for his "desires" was their answer. As far as we know, Josh did stop molesting his sisters, but he then brought the family down by taking part in the Ashley Madison scandal. That caused Josh to be dropped from 19 Kids and Counting, and when that didn't satisfy the public, the whole show was sort of cancelled, only to be revamped with a spinoff that Josh, JB, and Michelle were supposed to never appear on.
I don't know exactly what Derick was looking for when he approached JB, but he was happy to marry JB's daughter and promptly fell off the rails to screw it all up. He couldn't hold a job, he took Jill off to Danger America where she had a nervous breakdown, and when he returned he couldn't stop spewing his idiocy and hatred all over Twitter, causing him to be banned from the family business (aka Counting Down, the spinoff off to 19 Kids and Counting).
Ben also initiated contact because he was interested in Jessa. His father pushed the deal because he had thoughts of somehow profiting from the Duggar connection, only to find that the Duggars have an innate sense of when people are trying to horn in on their business and if they can't use them, they freeze them out.
Jeremy approached Ben and Jessa at some sort of religious thing, got introduced to Jinger, then made his way to JB and played his part well enough to get JB's approval to marry Jinger, but I suspect that even before the wedding JB had misgivings. He was probably too far into the deal to back out without a good reason, and the die was cast.
After that, JB was probably thrilled when Austin wanted to court Joy. He'd known the family for years and even though Austin only had one sibling, his parents did appear on a reality show titled "World's Strictest Parents". The boy knew how to take orders, his parents were part of JB's church, and Austin has an adversity to creating drama and drawing attention to himself. He might not ring up JB for advice on what to order for lunch like some of the other kids, he doesn't appear to like being on camera, and he is more of a loner, but Austin doesn't seem on the path to bring another scandal down on Duggar heads.
I think that JD really did find his bride all by himself, but I'm not sure on how his younger brothers ended up with their mates. JB is nothing but determined, and I wouldn't put it past him to continue to push marriages on his children as quickly as reasonably possible.