Congratulations on your purchase. If I may "hijack" the thread for a bit, how do people keep in practice with a HD shotgun? Do y'all shoot trap and skeet even with the disadvantages for that purpose? Somehow, I can't picture myself going to the range and shooting at a patterning target every week.
Same way as with a pistol for me practice emergency reloads. Target acquisition, dry fire. Maybe take a course
^^^ this is how you start. Get snap caps because most of the issues people experience with shotguns is (1) loading a tube mag; and (2) operating a pump quickly without short strokes. Once you've gotten to the point where you're comfortable loading, dry firing, and operating the gun, and maybe taken a class, there's "practical shotgun" and 3-gun and 2-gun matches.
Practical shotgun is basically what it sounds like, practical use of shotguns that aren't oriented towards trap, skeet, or sporting clays. Most of the matches I've been to and heard of involve shooting birdshot at steel poppers, clays, and spinners, and slugs at steel plates. Usually, buckshot at matches isn't a thing because of concerns about damage to targets/backstops, how far the shot can travel, and its a lot more expensive than 7.5 to 9 low brass birdshot.
3-gun is pretty well-known, but for those who don't know, its a match involving the use of a pistol, rifle, and shotgun. 2-gun is similar except its only one long gun and a handgun. While most 2-gun matches are rifle + pistol, shotgun + pistol matches are popular here in RI at some clubs because the clubs only have so much space and birdshot doesn't travel as far as a rifle bullet.
Of course, this isn't to say that trap, skeet, and sporting clays aren't good practice to become familiar with a shotgun, but you should consider why those more traditional sports exist. Trap is descended from live pigeon trap shooting in the 19th Century. Skeet started in the 1920s-40s, in fact in the Northeast, in response to how trap was less practical of an experience for upland hunters. Sporting clays is often called "golf with a shotgun."
Practical shotgun and multigun matches are probably the best way to understand the ins and outs of defensive shotguns, absent a very advanced class.