As you near the end of this sensual blow job, make sure that your mouth makes the cock wet enough so that it can easily slide into your slutty asshole. Once it is wet enough, put the cock down on the floor pointing up and gradually position yourself above the cock so that your asshole is positioned directly over it.
Once you are in position on your knees above the cock, lower yourself on to it. Feel it as it penetrates your most private hole. Feel it is it stretches your hole as you lower your body onto it. Yelp with ecstasy as your whole is invaded by this cock. Moan with pleasure as your ass is filled with cock.
After your ass adjusts to the cock that you are now above, begin raising and lowering your body so that the cock that is sticking straight up in the air can penetrate in and out of your ass. Moan with ecstasy as your ass pleasures that hard cock. Put your hands on your nipples, your head or above your head as you ride that cock.