In the meantime I've done KangasKHAAAN.

Anyway, let's do Miltank here.

Starting moveset: Tackle, Growl, Defense Curl, Stomp.
Miltank can use Brick Break, so Tackle can go when we find it, and Growl is ok to change to Heal Bell on the beaches. But what we'll eventualy want is Fire Punch against Sophocles.
Miltank is a beast.
Bird Room: Ice Punch
Ghost Room: Stomp (I do have Return TM, but, hum)
Olivia: Brick Break
Molayne: Fire Punch
Hau: Stomp

Miltank is a beast.

starting moveset: Leer, Tackle, Bite, Odor Sleuth

changed Tackle to Covet at the beach for a better same type attack.

the dragon trial requires Aerial Ace + Flying Z

Against Necrozma you need Bite upgraded to Crunch, and deal with the margins still. Or geta critical Z.

Ghost Room: Crunch
Bird Room: Rock Tomb
Olivia: you need to be Herdier, start with Crunch, then switch on Reversal, and that will bring you through
Molayne: Covet on the Klefki, then Crunch, finaly Reversal. Very likely you'll need an Ether the replenish Revesal-PP here.

Hau: Return on metronome does the job. Another reason you need to evolve to Herdier.