This guy has a lot of Youtube videos about the subject. He's one of the few I can watch for an extended period of time.
This guy is pretty good, pragmatic and offers excellent practical advice.
There are lot of excellent HD slug, buckshot shotgun loads to be found in "reduced recoil", "tactical" offerings. This is where having pump action helps because weaker but very effective loads may not cycle through self-loading shotguns. If you have "Joe Biden" shotgun you can even use mini-shells offered by Italians, Americans (Federal Cartridge) and Mexicans (Aguila).
