Improving Blow Jobs?

IM
I've never been able to make my bf cum with a BJ. I get very self conscious. He just told me he would love a BJ where I stare into his eyes and cums in my mouth. I refuse to let him cum in my mouth. It's a big no for me so I told him he could cum I'm my boobs. He was fine with that. How can I improve my Bjs before I see him again? I wanna make him super cum. He tends to get very soft during a BJ after a while