I did a search and couldn't find anything on this. But during the daily quest for the Shado-Pan called "The Enemy of My Enemy...Is Still My Enemy" you're sent to pick up explosive Yuangol Oil and drop it on 100 combatants in a certain area. The oil is an instant kill to the combatants and each one that you kill awards you 11-17 rep with the black prince. Meaning killing all 100 will get you at least 1100 rep with him. You can then abandon the quest, pick it up again and kill more mobs for more rep.
EDIT: Because of other people throwing the oil too, some mobs maybe tagged to them so you won't get rep from all mobs.
Second Edit: This will only work until you hit honored with black prince. I just did and they've now stopped giving me rep