No, definitely don't use the same technique as a shifty. Shiftys execute exactly the same as a straight air, except you shift your body once you're in the air.
It seems your problem is the carving since you said you thought you were already carving.
From the video footage it doesn't look like you're carving at all, rather you seem to be sliding your turns a little or riding slightly on an edge, but not carving and definitely not creating much pressure.
I'm also assuming that first speed check wasn't a carve (on that note, try not to speed check so close to the jump ramp, you should already be on your setup carve by that stage).
My suggestion is to work on your carving technique on basic runs and practice building carving pressure to spin flatground 360s on greens.
You can do this pretty easily by picturing imaginary run-ins on green runs and pretending you're doing your setup heel carve then your toeside carve then releasing that toeside carve pressure into a 360 spin.
You should be able to feel yourself building pressure when you carve and that's the pressure you need to get used to using to spin the 360, rather than relying so much on spinning with your body.
Last edited by Jed; 12-29-2012 at 06:13 AM.