What tactics does Napoleon use when negotiating the sale of the pile of lumber?

In the book Animal Farm by Orwell, a pile of timber lies unused on the farm, left over from the days of Mr. Jones, and Napoleon engages in complicated negotiations for the sale of it to either Mr. Frederick or Mr. Pilkington. When negotiations favor Mr. Frederick, the pigs teach the animals to hate Mr. Pilkington. When Mr. Pilkington then appears ready to buy the timber, the pigs teach the animals to hate Mr. Frederick with equal ferocity. Following a slew of propaganda against Mr. Frederick the animals are shocked to learn that Mr. Frederick eventually comes through as the buyer of the timber.