What do I do with my friend’s dick?

Long story short I had an online friend and we planned to meet up at the end of the year (If possible). He is bi and we are extremely curious about each other’s dicks (He is cut and I’m not) and he is especially intrigued by my foreskin and wants to play with it as well as retract and help me clean it. We plan to go to a sauna together (completely naked), not only that, he is down to us hanging out with each other naked at his place as well.

My question is, what can I do with his cut dick like how he wants to play with my foreskin? How do I touch his dick to keep things fun?