Ok here's what you should do.
Carve about 80° when youre first learning them, then work on not carving as much as you get better at them.
Jump like you do for a 360. Tuck up when you hit 360 and keep looking!
Lean more forward when you start to go past the 360 because that will help you land, even though you don't spin enough. Atleast you will have less chanses of falling, haha
Try them down a cirb at first? thats how I learnd them atleast, then just take it to small banks and smaller cirbs untill you're basicly down to flat.. hope this helped

And yeah, try to throw your shoulders as much as you can to the side!