The only thing that you need for flirting is very simple, it's just a matter of tactics. You place yourself physically nearby and start commenting about whatever random thing is happening on the place, call it weather call it furniture.
You simply keep talking talking talking, if you don't know what to talk about ask questions.
If the person is attracted to you you will know, they will smile in a very characteristic way. Only if that happens invite them to do something with you. Something simple that doesn't clearly show it is like a date, rather an opportunity for keeping up the interaction. For example going to the café and having something.
If they are truly interested on you she will gave you all kind of opportunities to keep the interaction going, and escalate it sexually. For example by getting very physically close to you.
If that happens don't be ashamed whatsoever to show your interest back. At that point they cannot be scared of whatever you do about it, they want it. Touch them on simple parts of their body, like the forearm or the belly, or give them some small kiss on the lips, the same way you would do with a beloved one.
Your goal isn't to convince anybody, but to assest if they are interested back. Either they are already or they aren't, that simple.
The thing is most people won't show interest not because they aren't, but because they are also too shy. What they liked to have is the opportunity to get flirtatious without having the feeling they could be rejected anytime.