RE: MICRO BALLOONS
In addition to what saramos said about polyester resin, it will also dissolve styrofoam. Epoxy is much more user friendly for a beginner and it doesn't make the whole house smell like a auto body shop.
The catylist for polyester resin contains methyl-ethyl-ketone-peroxide (MEK peroxide), something that you do not want to get in contact with, especially not your eyes.