I’ve never had to bring something quite that complex to my group. But my method is read rules with the start setup laid out in front of me. Mostly, I don’t have patience for long rules and zone out for large parts of the reading. Then watch some play through/tutorial which I also don’t have patience for, so I skip parts, but keep going until I sorta feel like I get the gist. Then we play with everyone knowing it will be slow this first time, I give a few min sorta this is what we do, you’ll find out more later. And then we play and I reference rules often, but also do some GM fiat if not quickly clear what the answer is. Then finish, or quit early even if having fun if it’s a long game, once people are at the, okay I think I get it point. Then we play again next week and in between I look up some stuff I discovered I need to know in the rules.
Usually takes about 3 plays before I’m really doing most all the details right on anything more complex than say Castles of Burgandy. But that’s cause I’m real not interested in study, and no one else will do it. Have heard Gloomhaven family stuff is pretty amenable to guessing on some details and going with it cause not competitive.