It depends. Sometimes a little LITTLE bit of pain is actually enjoyable. I like when a girl sort of slurps up one or even both of my balls in her mouth, some guys will like that some won't. Licking the scrotum(ballsack lol) is also nice. The scrotum got lines on it almost like it is a burlap sack maybe trace along them with your tongue. Something the girl I lost my virginity did that I will never forget. We were having sex and I was doing her from behind and she reached back and cupped my balls in her hands. There was something very sort of romantic about it. All I can say is me and I think most guys like for a girl to pays some attention to our balls and not ignore them or be grossed out by them. They do look weird even we think so.
As a guy who absolutely LOVES this activity from a woman, I would say the best technique for me is if she mixes it up. If she just lets go of inhibition and gets playful with them, she can't go wrong. Suck a ball into her mouth, pull it gently, let it pop out; start batting her tongue gently back and forth on them; playfully lick underneath them; suddenly try sucking both into her mouth; let them pop out again and then start doing long licks up and down to let them raise and drop; back and forth between rough and tickling gentleness. If she keeps this up I will go crazy, start writhing, and be ready to do anything for her.
That said; I'd guess that that's just me and every guy's different.
I wouldn't want a girl to be very rough with my balls, because it is pretty easy to hurt them. I do like having them licked and sucked, but they are very sensitive, so it really doesn't take a lot of pressure for it to feel great.
My balls are very large, and I think it would be difficult for a girl to get one in her mouth. But if she could, I would like her to suck hard, and chew on it, then pop it out hard. I squeeze my balls hard, it feels good. So yes, rough is good. Don't listen to these pussies who are 'too sensitive'. They're just little boys. Try a real man, like me, you can chew my balls off any time honey.
i don't know how most guys are but I enjoy them to be sucked a little but never rough cus mine are kinda too sensitive for all that + I don't get turned on that much just from messing with my nuts
I say let him know that he can say when you are being to rough. They are sensitive but not to the point of where everything hurts it. Treat its sensitivity like eggs they feel like they can break and enough pressure will make it a nightmare. Its safe to say that you can ask him to tell you when it would be a good place to slow down or don't go any further. Sucking is nice but can hurt if to hard but I honestly can't see how any licking would hurt. Sorry if sounded perverted =/