Something that ive learned a little ago and showed to be effective:
Fill your body with AIR, but not the PHISICAL air, i mean de ASTRAL AIR.
See yourself floating in a deep universe full of air... as you breath, this air comes inside you through your mouth and skin, filling you, like you were a baloon.
This air makes you lighter, and you float. The more air is inside your astral body, the less heavy you get.
Hope to have helped!