You walk into a bar, where a group of white men who range from very young, barely in their 20s, to about 40, are going on loudly about the "black problem" in the town. You join in, making comments to ingratiate yourself, even though it feels like betrayal, you think of the coming payback. You make out like you hate people with even a little negro blood.
"I've got a way," you say, "of finding out who's got any negro blood in them." You think of the juice, but you also think of "other" ways you could spread the changes.
The men agree this is useful and invite you to their "meeting" later that night to test out this stuff.