Teaching a guy to dildo his ass

I love teaching a guy to fuck himself in the ass. I love telling him to relax himself and then to go in and out in the ass with the dildo. Relaxing the ass muscles is the key to making sure that the dildo goes in and out as far as it can go. Without relaxing, then the dildo does not go in and out that far. He felt like he can trust me and then have the dildo go in and out.