Not a good plan. You want it to be plain as day to that other person, that you are into them. That’s the whole reason why you flirt. If they’re not picking up on it, then your efforts are totally wasted.
On the other hand, if you want to keep other people from seeing that you’re flirting, that might be worth doing. This only really works if you know each other well enough to be able to share a subtext together. Then you can look like you’re having one conversation but actually be having another one. Such as when you’re working together. You could look like you’re having a conversation about work, but then work in some fun innuendo.