He's so eager to follow instruction, so completely willing to do whatever Ned shows him, and he hopes that makes up for the fact that he really has no idea what he's doing. When Ned shows him what to do with his fingers, he imitates the motion, remembering that Ned had done something very similar to him, and just how good it had felt. He wants to be able to make Ned feel that good, too, and the best way to do it is by learning from Ned, who obviously knows exactly what he's doing.

And from the way the motion of his finger makes Ned arch his hips and cry out like that, his instructions have been good. There's no way he could possibly resist doing that again, even if he wanted to, from the desperate way that plea comes out of Ned's mouth, so he does, and then he does it again, wanting to get more of those intoxicating noises. His other hand can't seem to stay still, either, trails its way across Ned's stomach, and for once, he's not saying anything at all, because he's so very focused on this, on making Ned feel good.