I play a character I think qualifies as charasmatic. At least, he is occasionally. Thing is I don't really think of him that way. I think, in general, it can be very difficult to play a character when you go into it thinking you're going to make them charming or charismatic or flirty or funny. I focus entirely on his speech patterns, what he talks about, how he talks to people, and how he uses his expressions and all that kind of stuff. Because, essentially, that is what makes him charismatic. It's not just a random "air" out of nowhere that someone has. It's actually a concrete, tangible thing.

And then it's basically up to the characters your character interacts with to interpret it in whatever way. Because the thing is not every character is all that perceptible to charisma. But then if no one seems to respond to it, you probably need to work on your characterisation.

But basically, as long as you do body language, expressions and speech right it should be doable.