There are many types of propaganda in Animal Farm - in most cases, the propaganda is used by the pigs to further their own ends and present their words and actions in a more positive light.
One of the earliest examples comes in Old Major's speech, when he calls all of the other animals "comrades" and presents himself as just one of the "plain folks", when really he has lived a rather privileged existence on the farm. He uses many "rhetorical questions" to get the animals on his side, for who among them can disagree with what he is saying?
Soon after the animals take over the farm, the animals notice that all the apples and milk are missing and are being consumed by the pigs. Squealer emerges as the chief propagandist, using "testimonial" arguments and telling the other animals the pigs need this "brain food" to help them lead the farm.
Napoleon and Squealer later use "name calling", "scapegoating", and "logical fallacies" in their representations of Snowball. They call him "traitor" and "criminal," quickly destroying his good name among the animals, then use scapegoating to blame every bad thing that happens on him (ie. the destruction of the windmill). They also use logical fallacy: Snowball is bad. Bad things are happening on the farm. Therefore, Snowball must be doing the bad things.
At other times, the pigs use "euphemisms" to put a good spin on some of the negative things happening on the farm. They don't have a "reduction" in food - they have a "readjustment."
The pigs also use "bandwagon" techniques. This is seen both when they teach the sheep to sing "Four legs good, two legs bad," then later, "Four legs good, two legs better."
One of the primary forms of propaganda the pigs use is "scare tactics/fear." We see this first with the use of the dogs to chase Snowball off, then later to force confessions from the animals. Additionally, any time the other animals begin to question the pigs' actions or what is happening on the farm, the pigs ask them, "Do you want Jones to return?" as if this is the only possible outcome of going against the pigs' decisions and wishes.
All of these techniques help the pigs to achieve their ends by blinding the other animals to their true purposes, actions, and motives.