What exactly do you do with his balls?

I've never really known what to do with them, so I just avoided doing anything. I'd tease him with gentle touching before going down, but then move my hands to his torso. Recently, I'm trying to learn what brings him more pleasure, asked about his balls, but he doesn't give me much instruction. Lastnight, I cupped his balls in my hand while wrapping my thumb around his dick, a good handful, pressed them into his body. He seemed to enjoy it, but I'm not sure as he didn't really vocalize much. What else can I do?