there are many things for femdom that you could try but does your bf have any fetishes related to femdom to try because thats typicaly a good place to start. honestly "femdom" is a very wide area to search for without narrowing it down first. But a good place to start is "what kind of dom am i" or "what kind of dom does he need/want"? i'll give a breif over view of how i see most female dominants in catagorys.
Does he want/ need a:
Mommy? (a dominant who basicly treats him like a child doing most everything for him)
big sister (a bit of a less controling but more prone to "pick on" and tease verbaly and physicaly then a "mommy")
dominatrix (heavy verbal and physical but your still doing most of the work)
mistress (this can be treating him like a pet, slave, or toy to use but he will be doing more of the work for you rather then him)
goddess (you have him basicly worshiping you doing whatever you want the only work you have to really do here is commanding him)
or some mix of the above a few dominatrix i've seen tend to mix with goddess and mistress catagories. Hope this helped!