I need major help with blowjobs

So I know it sounds bad but there is this guy I like and we've been playing around a lot. He does give me a lot of mixed signals so I'm not completely sure if he likes me or not or if because hes about to leave for work. But anyways if you ever been in a situation were someone keeps dragging it out and making you want them you will get me.

So anyways we have done some stuff and hes really into blow jobs (of course) but I'm mot really experienced with it and I want to do something that's going to blow his mind (if for nothing at least so he can stay thinking about it after he leaves as payback for the times he has left me thinking about it)

So I can't seem to do great everytime we tried. Like he has finished but I know it can be better and I want to be better

Like I really need help. What's the details on a great bj?