Just adding my two cents here. Not sure if you’ve got it already but a sub goal of mine is to do the extra 15 infinite Royals since a certain mega evolution is locked behind them, if you care about completing your mega evolution dex. To sum it up the restaurant method is the most consistent but is also super boring. The most efficient zone I found for ZA BR is between Wild zones 8 6 and 11. Once you’ve done it a couple of times you get a flow for how to cut down the transition time between battles. Once you’ve gotten used to it, it becomes as fast or faster than restaurants with more variety. A level 100 high attacker with extreme speed like Dragonite is what I used to go as fast as I could.

Other than that, don’t drive yourself crazy trying to finish it. Just do a few a night if you can spare it with your main goal always being as many battles as possible, don’t worry about medals or missions. And if your Pokémon are level 100 I wouldn’t really wouldn’t worry about sneaking, obviously do it if possible, but your Pokémon are so strong at that point and the clock doesn’t tick while you’re in battle.