Soometimes I focus on just breathing in and out, sometimes nothing, sometimes a specific object. As you practice and try different techniques you will find what works best for you. And it may not be the same technique all the time.
Sensei actuall did begin to stock the female groin guard for the girls. As odd as it felt the first time you sized one of the boys up for head gear, hand pads and cup it felt really funny handing a girl one too.