That's it, slave. Now kneel for me, and make sure your balls are resting in front of your bound legs.
Use your dominant hand to grab a wooden spoon, and use your non-dominant hand to ensure that your cock does not get in the way of you whacking your balls with the spoon. Do this 20 times and, most importantly, keep a very strict rhythm. If you are even a split second late with a whack, start again until you get it right - and make sure smacks are hard, slave.