Angels are advanced technological beings who are messengers of the gods. These extra-dimensional beings are large, upwards of 30ft tall, and resemble eldritch abominations in their true form, such as three faces, wheels, wings, etc. As they are monstrous and terrifying in appearance, they take physical human form when they enter the material realm. They can travel between realms, but cannot control a human body from their realm, and must be present in the world in order to have any impact on it. Specially built physical bodies are built to house them so they can interact with mortals without giving them a heart attack from fright.
It stands to reason that for a being of that size, it would naturally have to take a form of similar size. The problem is that thirty foot tall beings walking around is not productive for a relationship with humans. These physical forms must be human sized in order to interact on a regular basis. therefore, an angel's physical form would have to squeeze into a body with a much smaller mass, volume, and size.
What would be the best way for an angel to make this possible?