I just recently started working in one of those Student Homes (or how do you call it) where I take pictures of students (19+) for some card they need to buy meals. Along with this, in my spare time, I get to stand around chatting with people or giving them directions etc.
I tried to keep it professional but there are just so many girls flirting with me. Already got 3 numbers in last 2 days but kept it safe (so I don't get fired and stuff) with only the girls who were obviously into me heavily.

Just some things to have in mind, because it's quite specific situation:
1) I'm allowed to do this as long as they don't report me for harassment.
2) I have to actually do my job from time to time, so my interaction time is random, ranging from 2 to 10 minutes.
3) Picture taking and other stuff I do takes around 1 minute per person, so I guess I can make her wait for me while I finish.
4) Possibly irrelevant, but there are usually 20 other people in the same room as the two of us, including my colleges.

So, how do I escalate the interaction quickly to get a number, without being too pushy? I kind of want to keep it casual but direct and fast paced at the same time.