I will never be on Jibaku's or Trickroom's or whomever's level, but I like to think that I'm an ok player.
The best, and most accessible, way to get past Multiscale Lugia is Toxic. Even strong special assaults bounce off it, you need to use Calm Mind if you want to get past it that way. Pair Lugia with a Darkrai check like Fightceus and you already have a good team hehe.
I think that speaks volumes about how great it is.