Don't try to do "Regular" Universal attractions during the HHN Hours. If it is in your budget, buy a day admission to Universal and visit all of the attractions during the day. In past years, if you are in the park when it closes and have an HHN ticket for that same night, you are allowed to stay in the park will they shoe out all of the other guests and wait for HHN to begin. There is about one hour between regular park closing and HHN opening. While in this HHN Limbo, you are able to have first access to all of the HHN Haunted Houses and Mazes before the crowds rush in.
HAVE FUN