start pulling your knees up to your chest during your spins. Once
you've got that, go for the grab. I learned mutes first, but I'd say
start with safetys. Make sure your grabs are at a point where you can
just reach down and grab without really thinking about it during
straight airs.
For 5s, don't think about them like 360 + 180,
or you'll stop at 360 every time. It's a lot easier to think of 5s as
180 + sw 360. It's also easier to hit a bigger jump than try to spin faster on a small jump.