When I go to Horror Nights, I wait in the park after everyone leaves. If you have the hhn add on to your normal ticket, you just wait in the park. There are two holding areas to wait in, one by Finnegans and one by ET. I wait in the one by ET, and I'm able to get the parade building house, both tents, Disaster queue, and at least one sound stage house done before the lines get above thirty minutes.
Following this plan, I've been able to get every house done in a night.