a couple years back, i remember having trouble with 3s.
i built a jump on a golf course down the street and seshed that for a couple hours and learned it.
you need to remember to prewind tour body/arms the opposite way u are going to spin before the jump, then pop at the lip, and spin your natural way, because of the prewind you will have more power for spinning. and remember to look with your head!!!! where your head looks your body will follow, so look over ur left shoulder if u spin left, right shoulder if u spin right. you will be blind for a sec, bet keep lookin for ur landin, at 270 u will see it and slow down your spin (this will happen automaticly) then stomp it!
good luck!