I do not find oral sex dirty or gross or even unpleasant. As a matter of fact, I love it, giving and receiving. Although I am primarily a sub, one of the things I love about giving head is the sense of power it gives me. I have his full attention; I am the one causing his moans, heavy breathing, words of praise or of religion found (Oh, Goddess! he might cry out) I hold in my hands and mouth either/both pleasure and pain (my guy likes a little biting, which I have found fairly rare.) Precome, to me, is salty, almost like tears, and I love that flavor. I love the musk smell of his whole genital region, as long as it's fairly fresh. What I didn't like was the taste of come--I had a bad experience once in which I surprised him by going down on him and he surprised me by coming almost immediately, with no warning. After that, I didn't spit or swallow; I ducked! My current lover/Master is always so generous, whether top, bottom, or vanilla, that I wanted to do more for him. Right now, he still tells me when he is about to come, pulls out of my mouth, and comes on my breasts (tit-fucking is one of his favorites so seeing his come all over my chest actually adds a little for him, I think.) Then, I use my fingers to bring his come to my mouth, a little at a time-at my pace, not the fountain of an orgasm. I am learning to enjoy his flavor, and I am hoping soon to actually say I swallow.
If you really want to do this with/for him I'd start at kisses, move up to licking, then taking him into your mouth-oh, and don't forget that most guys like some attention paid to their balls, too, not just the cock. Ask him if he can tell you when he is coming; that way, you are not surprised by it, and can decide if you want to spit, swallow or duck.
You might also want to try a 69; I'd recommend you take the top. That way, you get some return pleasure, you have more control over how much of him you take into your mouth vs. you being on bottom, and if you are like me and love to be spanked, he can get in some swats while you nibble each other.
Another thing: listen to him, in two ways. First, ask him what he likes and listen to his words. Second, listen to the sounds he makes while you go down on him; the sounds will give you some pretty good clues as to what things you do really rock his world. Since all of us good subs want to please our Dom/mes, hearing his sounds of happiness is really rewarding.
Hope some of this helps-and, gentlemen, could you weigh in on whether what I've said sounds good to you? Thanks in advance for the feedback.