Yes, the flange goes on the inside, and the bolt head on that end too, with the nut on the "outside" of the car. Consider the scenario where the bolt rusts in to the centre of the bush - with the flange and bolt head on the inside, a sharp belt will remove bolt and bush to allow the subframe to be removed. The other way around (the way I have it
) means that cutting is the only option. Obviously your bolt won't go rusty, and the centre isn't bonded in to the poly bushes anyway...
I used some washing up liquid, but I've since been reminded about the salt content in that so perhaps you could use Vaseline or something similar, or as you said soak it in warm water for a bit. I used the mounting bolt to pull it in, with a big washer and a sleeve around the outside of the subframe to allow the protruding bit. But mine were NOS rubber bushes, not poly.