Restrained for Frustrating Handjob Ruined Multiple Times

My chastity sub hasn't been milked for a while, so it was time to empty his balls without any form of enjoyment. For his milking I restrained him naked to the top of the stairs with his arms behind his back and blindfolded him then proceeded to stroke his cock right to the edge, slapping it when it got close to the nice bit and letting it bounce around on its own until it calmed down before edging some more, always stopping just in time, making his man muck fire out of his twitching cock without orgasm. The longer it goes on, the more sensitive his cock becomes and then its time for some post orgasm play, making him squirm with the slightest touch.