Its not a terribly complicated build, getting the units themselves is also not to hard as none of them tend to be heavily contested. The biggest issue is you need the stars to align for you to get the swap hero + at least dragons/demons and ideally beasts as well for parrot.
Than the other key is to rush to and than stay at three stars until you get the dragon. Once you get imp and dragon you intentionally want to keep a smaller field to ensure imp goes onto dragon.
While still waiting for the parts of the combo murlocs and anything else that gives field buffs pairs well with the hero since temporary buffs become permanent on a swap. Keep in mind you can also swap stats with stuff in the shop for an early boost to your units.
I have pulled it off a couple times my self, although never got as big as the one I posted.