Mine just pace and eventually break from their broodiness in a separate pen. I don't know how to convince them to set where I want them to set. I'm gonna try again after we butcher out the extra rooster who's occupying a pen I need.
My nestboxes this time of year are like clown cars too. My cochins go broody pretty quickly, and always start young, now if I could convince them to set where I want them to, I could make use of them too.
Cochins are loungers, generally it's a prequel to being broody. If you watch your hens long enough you will notice hens that go broody will take longer than hens that are just getting that egg out and have no interest in being a mom.