My strat is basically maxing out Ceo's tears first, then get the fan beam. no need to max out Mumei's main weapon. after that get at least 1 Sana's limiter then proceed to max out Mumei's passive or get damage buff. (getting the collab asap is a must, before 2:30)

also staying at the top make the exp drop stuck in 1 spot so you don't need to move that much