It looks like your spinning with your legs instead of your core (the midsection of your body). This is easy to do on small spins like a 180 but as you get in to higher rotations a lot of the force will need to come from your core. If you load your core and release as you come off the jump your body will spin and the board will follow and your rotation will be much faster.
Is it easier to do this with a grab? because i try to use my upper body and i end up leaving my legs behind. If i try this and just grab the front of my board will that help keep me together?