Bubba was neutered at 6 mo old. I never saw him hump until he was about a year and a half. Now, after dinner (never after breakfast) he goes and finds his donut bed and has his way with it. Sometime just a short hump but sometimes all the way. He will walk around hunched over. It using resolves but when it doesn't he has to be checked. If his hair is too long it can be trapped. Usually, a cold shower
will work (only kidding). Some people use sugar.
Oddsock, if this happens again, I would buy a water soluble lubricant, such as surgi lube or one of the female lubricants. Vaseline is not water soluble and may cause problems if used internally.
Bubba is 9, now, and it is his favorite after dinner activity. My husband will occasionally ask him if he would like a cigarette
. The only time it is a problem is when we have dinner quests.