Scrumptious, I totally hear what you are saying! Mr M was not exactly well versed in the aural arts when i met him, and I did feel a complete pratt at first. I decided that the first thing we needed to do was name our bits ( no, I don't mean Florence or Fred) and find a vocabulary we were comfortable with. This sounds simple in practice but I spent ages working out what I was going to say to him to raise the subject in the first place. Funnily enough, the words we chose 13 years ago are not the ones we use today- we're much more dirty now!
It then was easy to say things like "I really want to suck your dick" and from that it was just a short hop to throwing a few adjectives in and describing what it feels like, tastes like, make me feel etc.
After that I read some erotic literature aloud to him to see if it went down ok and the rest just followed on from there.
Now we talk dirty all the time and it forms a huge part of our sex life. I think it works best if you can tap into the shared language you create between you to make meaning of circumstances and situations- that way it really is YOUR dirty talk and not something imported from a Sin Cities Mega Fuck film.
PS it helps (both of you) if you can visualise what is being said and supplement it with physical actions.