Don't talk. Please, don't talk. By talking, you are assuming it is something "dirty" that must be discussed. How would you like it if she said, "Honey, I just want to let you know that I don't mind having sex if you are really smelly and sweaty in the crotch area. It really isn't too gross. So, is that something that you are into that I just didn't know about?"
Ask for her assistance with your own O and then make your move. And while I agree with the towel comment, you may want to put penetration to the side until things are going really well (which could be right away, who knows).
