Now for a little pain. Leaving his blindfold on, grab the ruler, and use it to tap his balls and the head of his cock. Start reasonably gently, but ask him if he likes it, and ask him if he can take it harder. Ask him to beg you to hit him. By using this strategy, you should be able to get to a level of pain he is comfortable with, without causing any damage. In arousal, he will be able to take a lot more pain than usual, and he’ll probably find it turns him on even more.
Alternate between slapping, flicking and ruler tapping his balls and cock head with some more paling and the odd bit of stroking of that cock head to drive him crazy.
Once you’ve had enough fun like this, for as long as you want; the longer the better, click next.