Your guy is laying bottom up. You pin four or five fingers at the root of his scrotum and scratch delicatly, lovingly, in the direction of the balls, then back up, then back down... You proceed softly, but you manage for his balls to feel clearly your fingers scratching them from the back, of even from the front.
He was displaying his ass and balls to me. Bottom up on the bed. First, I licked his balls softly, from behind. When they were all wet, I sticked my lips and tongue in his adored slit-ass. I then did some scrotum combing on his wet trembling balls. I was licking and combing softly, getting hard myself, dreaming already to fuck his adored cock hungry ass.