
You can do it a few times, but I would not chain more than three together (if you chain them, I would treat one chain as one whack). When I say chain, I do not mean in really rapid succession. The pain (for lack of a better word) from the "whack" moves to other parts of the body, but it does so pretty slowly. I can't tell you how far apart the whacks should be in terms of seconds, but there is definitely an appreciable amount of time.
Don't over-think it though. You have great instincts, you will be fine. The first time my GF did it, she whacked me three times, with some pause between each whack, and it was great. The first one will catch your guy off guard, the second one will confuse him ("did I just like that?"), and the third will hopefully answer the question in the affirmative!
If he ends up not liking it, it will have more to do with him not liking the act in general as opposed to you doing it wrong.
Also very important. I like it when she does this in the 69 position because it gives me something to latch on to when she whacks my balls (helps to cope with the pain). Even though I have no problem lifting my GF up off of me, it does make escape a bit harder and just adds some resistance to any involuntary flinching. This is important because even if I want her to stop, she can still whack them. If I say "ow" or "stop," it is not done so as a roleplay like I am beggingmfor mercy. It is usually said involuntarily. She will continue to whack, and to be honest, I am glad she does. It is one of those rare instances where "no" means "yes."
What brought about the discovery of liking this behavior is our use of the 69 position. I do like giving her oral in that position; however, as you know, I really hate BJs. She knows this so she just uses her hands to caress me or uses them on my "stuff" and, eventually, it all lead up to whacking.


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