i got a few tips for ya
first, its easier to do them when your going off of the noll of a jump (not the actual jump, but where the table goes to the landing, there is the sharp change in angle and right there its easiest to butter off of (that, or a similar hump of snow, but rember, the steeper the better because you pop out of the spin more on a steeper one)).
you should go into it with speed (not super fast, but its easier when you have some speed)
i find it easier to get yourself sort of in a snow plow stance, then wind up to spin, but dont throw your body forward, throw it to the side (the snowplow helps get your body to the side) because once you start your spin and get up onto the tips of your skis for the butter, you will already be about 90 degrees into the spin. at this point you should be 90 degrees into the spin and up on your nose. when you come around to about 180, maybe a little more, you should now come off of the lip/noll and you will sort of pop out and get a 360 around (you gotta time it so that is when you pass over the noll though). from there you just take it around to a 3, 5, or however much you wanna spin.
just play around a bit with it and you will get em.