Advice for beginner?

So I've only been in bed with one other guy besides the one I'm with now. The guy I'm with now has asked me to spit on him and shame his cock during sex. I don't know what the official name for this is, I've tried googling it and not much luck, so I thought I'd try here. I've seen humiliation play, degredation, and some other things but still not sure exactly what to call it. He says he's never liked his penis and he just wants to make his partner feel good, and that's pretty much what I read about people with this kink. I've never done it before, my last partner was always in need of reassurance, so this is a complete 180 for me.

The sex is amazing and I don't want to ruin the relationship between us. I really appreciate how honest he was with me. He told me some other stuff that he's into, but that's not the point of this post.

I just need some advice on what to say to this man in bed to shame his cock (which is difficult because it feels so fucking good) without making him feel bad and without sounding stupid...