I would suggest either buying yourself a fleshlight and trying with that (which, fine, is just a sex toy, so the sensation WILL be different, but it might help you get used to what it's like) or, failing that, take your time, use
plenty of lube as I'm sure you yourself will already be familiar with as you've bottomed before and, since he wants to be the bottom (assuming you're comfortable with being the top of course), engage in what I call "natural domination".
Natural domination is NOT the B&D kind of domination everybody has heard all about with whips and chains and saddlery, NO. NATURAL domination is the gentle domination of the sexual experience by one party, and the gentle submission of the other during the same experience.
As the top, I think it should be you that naturally dominates, so as important as the penetration (which should be slow, deliberate, complete and considerate - you're taking him after all), you should make eye contact (not 100% of the time, but DEFINITELY during). You should remain close. Kiss him during the act as well - don't ram ANYTHING into him - make love to him. Make him feel special, make him feel the emotion, and make him feel the moment.
I should direct porn ... hahahahaha
!?!?! Shadow !?!?!