Use lots of lubricant. Honey is amazing. Smear to heaped spoonful all over his cock and balls. If he is not totally erect do more licking than sucking. When sucking occasional run your finger around the base of his cock in circular motions.
Gently massage his balls. Try putting both his balls in your mouth while his cock dangles in your face. Lick the balls when they are in your mouth. Use your hands on his cock as well. Use your tongue while his cock is in your mouth. Change frequently between licking and sucking. Use lots of sexy talk as you hold his cock about one inch from your mouth. Tell him how much you like sucking his cock. Rub the area behind his balls (his perineum), scratching very gently between his balls and manhole. For a short time lick his balls and the inside of his thighs but stay away from actually touching his cock.
Put some ice in your mouth and continue sucking. Always remember the technique is to simulate the way he wanks, your lips need to become his hand. Your lips need to suck as he would wank. If he wanks watch think, his hand is your mouth. Pay attention to the rhythm he uses. Does he work the tip or the entire shaft, or both, and in what proportion? Which side of the penis does he favour? Simulate that action as best you can with your mouth.