Girl works at my job. I see her occasionally (maybe 4 times of chit chat)and we talk sometimes but very brief as we are working and our breaks never coincide. I can tell she is interested so next time I see her I want to get her #.

Is it advisable to, next time I see her, just be like "Hey, HB. We should talk more, let me get your #?"

I like a decent casual number close where as we are parting ways I just say "Hey, if you're thinking about me later, give me a call." If shes into you she'll ask for your number or offer her own. But if she doesn't its no big deal and not awkward and you haven't lost value. Or you can just go ahead and say "Hey I've been wanting to check out this sushi place over (wherever) but none of my guy friends will go, you should keep me company." If she says yes just say "Alright I'll give you a call when I get hungry", pull out your phone go to add new contacts, hand it to her and say "Take care of business." At any rate, keep the exchange casual since you work with her. Both of the above are a good framework.