Oral Sex: how to tell if he's satisfied?

[tigereyes12]

For the men (or women from experience): can you finish even if you aren't enjoying a blow job, or are there certain things you do if it isn't good? Is thrusting up a good or bad sign? Grabbing the back of the girls head?

[Eweezy]

I personally put my hand behind her head and grab her hair softly. I also move her hair away from her face. I wouldn't thrust up and down because it's a turn off for me to hear a girl coughing while shes giving me a bj.