I have found that the best method to capture a planet is to build 100 assualt transports, set them to wall, and capture planet. I have captured many homeworlds this way.
Sure I lose many of these ships, but it is sooooooooo cool to see the planet captured with all of its defenses and facilities intact. And as a rule, 105. Troops are a cheap expendable and renuable resource. Use and abuse them.