Sweetened Blow!!
Good oral lube, no sugar (so you don't have to be as worried if you get it in your ta-ta), tastes pretty good, not too goopy, reacts well to saliva, gets all slippery so you can get some major hand action going... basically there's nothing bad I can say about it. It makes BJ's feel really good (or so I have been told) and it makes for a lot of sliding and oral fun!
Anyway, with BJ's you shouldn't just be using your mouth, if you are, like has been said, it's not fun. Use those hands and that tounge! Also, if your guy is really big, you might not be able to get him in your mouth without feeling like you have your lips wrapped around a fire hose! Try frenching the underside of the head (the sensitive part) while stroking him up and down with your hand!
I've apparently been blessed with all the amazing BJ giving genes here on TFP- I've never had a problem giving a blow job, not lockjaw, not numb lips, nothing. OH, speaking of numb lips... Is that because you're wrapping your lips over your teeth and then sliding up and down the shaft? That'll make your lips go numb for sure! Perhaps you should get an instructional video-
Good Vibrations has a good selection of staff-recommended instructional vids. Everyone can benifit from advanced sex ed!
Perhaps as a follow-up to
this little exhibition of mine (NSFW) I should do a thread on BJ instruction.... I think we all should... we'd probably learn a lot!!