Because I had never done this maneuver before, I actually thought about should I spit on my thumb. But, events moved so quickly that I didn't have time. And it turned out to not be necessary. That Pit Bull released so quickly I barely could jump out of the way while the owner was dragging him backwards and out of the gateway and the fight.
I have excised the anal glands on pet dogs before, so had some experience with the rear end of dogs. I think that doing the anal glands can be far nastier than just ramming my thumb up there.
BTW, I have meant to make this comment before, but I will use this opportunity to say this: A couple of posters have said something like, "If your story is true.......". I can assure you that as a former Explorer Scout and Law Enforcement Officer that every word of my story is true fact. .... On my Scout's Honor. There were many witnesses to this event, but I'm sure that none are current members of this forum.