You have nothing to worry about. You're a nice guy and that's really all that matters. As was already mentioned, the ladies here are very good at putting their clients at ease and making them feel at home. If you are respectful, on time, have good hygiene, and the proper donation amount that's about all that factor's into it.
In fact, one of the best times I had this year we probably said less than ten words the entire session. It was pretty amazing. So great conversational skills are definitely not required.
But if all that doesn't help your confidence, I will give you my secret weapon in being able to talk to girls. Please don't tell anyone - as this is a most powerful tool. Are you ready? Good. Listen close...
Women (yes, even the very beautiful ones) are just people. That's it. They are human beings and they live in the same world, they have (basically) the same needs, desires, fears, and frustrations we all do. They eat much of the same food, watch the same things we do, hate the same politics, and despise the same traffic. Many of them even laugh at the same jokes (although admittedly that is very ymmv LOL). We (men and women) are much more alike than we are different. Except when it comes to our naughty bits and the wonderful way they compliment each other. That's when the real fun begins...
So be yourself, don't overthink things, and if you do feel like talking - just talk to those girls like you would talk to anyone else. But maybe keep the fart jokes to a minimum around the ladies - for some reason they don't seem to appreciate them as much as us guys do.