history

There's the oldschool PR stuff like that of Edward Bernays' (may he rot in piss for all that he did to Guatemala and women).

There's the newer era of propaganda tactics that are countercultural and draw heavily upon the works associated with Letterist International and situationism, particularly Debord and the concept of détournement.

Then there's the in between space that is like Soviet realism art and things like protest slogans that aren't really in either of those camps, generally speaking, although a protest slogan is a lot like an advertising jingle I guess. You also find a lot of performance art-related protest stuff that falls into this space too. Art theory comes into play here oftentimes.

For media literacy there's Inventing Reality by Parenti, of course, and less great is Chomsky's Manufacturing Consent. There's also stuff like Lies, Damn Lies, and Statistics by Wheeler.

I think that one of the best tools for countering propaganda is having a solid grasp of logic. As in, doing a free online university course in logic and not like "searching up which logical fallacy I can shoehorn your statement into fitting" kinda logic; if you can trace out an argument and how it is framed then you are in a much better place to identify counter propaganda. It's also quite fun once you have a solid grasp of the basics of logic because a lot of people don't, especially R*dditor types, and you can usually run rings around that type of person because you'll be able to deconstruct their argument and identify where they're signalling that the argument is heading and you can pre-empt it (or even get them to agree/disagree with a proposition which will later undermine where their argument is going), which is kinda fun to rub in people's faces if they're being shitheads about the whole thing.

Depends on what you're most interested in and where you want to take it. Any study in English, philosophy, sociology, statistics, psychology, art theory, media studies, and history can all be used in service of either creating good propaganda or countering propaganda. (Well, almost any)