You can do this next part with your finger, or an object of some type.
You're going to fuck his ass with something! He may resist at first, they all do, but he will be pushing back wanting more before you are finished.
Get a dildo if you have one, or something similar. Maybe a bottle (wash it first), or a carrot (also wash), or just your hand. If you have some lube, use it well. If you don't, use spit. You can put whatever it is in his mouth first. Tell him to suck it like he likes you to suck his cock.
You could use it on your pussy first if you want to give it some added taste for him. :)
When it's lubed and ready press continue.