How do you hump a pillow if your a boy?

Guys, and girls, can hump a pillow in many ways.

The easiest way would be to use the pillow as if it is the body part you imagine focussing on during sex, which can be anything (whatever gets you going), put it wherever you want on the bed and start 'humping' it, keeping your penis between the pillow and your tummy. The pressure coming from that is a bonus to the friction of the pillow (and foreskin).

Another way is, if you are well endowed or, alternatively, have a small pillow, by putting your penis between the pillow and the rest of the bed. This might make a more realistic 'hole' to enjoy, but you'll need to keep your hands on the pillow to keep the pressure on it and keep it in position.

There are products which simulate a human orifice which can be use similarly (ass, mouth and vagina), which will definitely give you a better experience than the above examples, but with a cost. And don't forget to clean those after use...