I can say that no one is ever comfortable with dirty talk in the beginning. If there are people who are okay with dirty talk from the jump, I don’t know them. All I can say is that it takes practice. Let’s start with what to say…
Do you ever sit around with your girlfriends and brag on your man’s aesthetics? Is there one particular body part of his you are really attracted to? Can you wash clothes on his abs? Do his hands make you fantasize about what they can/have done to your body? If any of this sounds vaguely familiar, start there. If not, there is the old faithful commentary: talking about his penis. Men will never tire of a woman telling them good things about their penis...or their performance for that matter. If you have ever watched Sex and the City, there is an episode where Miranda is trying to figure out the same issue. It’s Charlotte that suggests just calling a man 'fucker’ and telling him to give it to you harder. You could also try commenting during sex about something he is doing that you really like. Tell him while he’s doing it that it turns you on, makes you hot(ter), etc.
If you are worried about being embarrassed while saying these things to his face, I want to tell you not to feel that way. This is your man. You should be able to laugh during sex with him from time to time. More than likely, any attempts at dirty talk and meeting his needs will be met with resounding excitement. However, if you are still uncertain, I recommend that you start by sexting. Since it seems like you are having difficulty verbalizing, perhaps the added buffer of saying something risqué via text without having to look at your man directly while doing it will assist you in getting the words out. Send him a naughty message while he’s at work about what you want him to do to you when he gets home. You could remind him how he did something great last time you had sex, and you can’t stop thinking about it. Even if you simply tell your guy that you can’t wait for him to get home to make love to you again, it is a start in the right direction. He’ll be pleased because you tried.