Well everyone is different. I'd start really gentle at first and then maybe gradually increase the pressure. Just make sure you're paying attention to how he reacts to it and talk to him about what he likes.

Well, if he goes ow, that's a good sign that's too much pressure. lol.
I apply a little bit of pressure and massage them but like not an abundant amount. I'm not sure there's anything I can compare it to really.

Squeeze them really hard. Oh erm, no, sorry got that wrong... make it gentle sounds most sensible.

I suspect this is a very individual thing. I recommend trying various things but trying to sense which he likes the most. Ih he is like me he will moan more if he likes it. However, please note, if his moan is more of a high pitched yelp.... definately a sign you need to relax your grip.

Them babies are sensative!!!!