I think they either have it in them or not. With so many breeds being bred for growth and egg production, broodiness is being bred out. In a producing situation it is a highly undesirable trait. The main factor being that one broody hen can jump start other hens. I saw that first hand with my own flock. I had one and then when the other hens saw that she had peeps, well, all bets were off. I had broody hens fighting with each other, broody hens disappearing into the woods, broody hens taking up every favorite spot for eggs, and then once the peeps started hatching they all had to be separated from each other. One mama tried to kill anothers peeps, and then went after the other mama. Then it became clear that some mamas were only good sitters, and really didn't care about the peeps past 3 weeks or so. Some mamas took good care of the peeps, and some after 4 or 5 weeks tried to attack their own peeps!
Well, you get my point. It was a hell of a year that year! And in the end, I had 75% males hatched. That was a lot of fun.. <<deep, dark sarcasm>>
I would say the only thing that you could do to try to draw out the inner broody is set up a great nest, filled with straw in a secluded spot and fill it with about 8 fake wooden or ceramic eggs and see if anyone bites. I have also had good sitting hens that didn't really take it seriously. They sat on the nest all day and they seemed broody but when something hatched under them, they ran away terrified and left the peeps to me.