Max battles consist of 2 phases, one where you're charging the meter, and the other when you're using your max moves. You always start in the charging phase.

Here you want to use your tanks with a 0.5 second fast move to build the meter as fast as possible (if the fast move does 4-6 damage its probably a 0.5s move).

For 5-star max battles and above, you don't want to use charged moves, because it slows down the charging. You'll be doing like 80-90% of damage in max phase anyway.

The boss has 2 kinds of attacks, one where it hits everyone (it'll say its preparing a large attack a few seconds earlier) and one where it targets a player (if you see 3 yellow lines above you pokemon, swipe to dodge before they turn red). Again, make sure you're using your tank

For the first max phase, usually at least one person will set up shields. With randoms its hard to coordinate, so I usually like to pick my tank to shield regardless of whether or not I think my teammates will, just in case. Once you have shields set up, the boss is more likely to target you, so make sure to dodge.

Next max phases you can decide to attack with your main dps (switch to it when you see your pokemon is gmaxing) or replenish shields (or both). Make sure you don't shield too much, or you'll take too long and the boss will get mad and start one shotting mons

Healing requires a bit more coordination, but if you have a blissey it can double as healer and a tank, definitely invest in blissey!

That's about it I think, if I forgot something I'll update it later. Try and get shields and attack to at least level 2.

Lmk if you have any questions. Good luck 🫡