Be patient with it, spin THEN grab. Also try to keep your chest straight by not reaching for the grab, this will help you stay on axis and not cork the spin.
if I can give an advice, being small in the air, like bring your knees up, definetly helps grabbing specially with mute grab. it also give the spin a nice style.
I have big problems with this too. Try crossing your skis or bending your knees to help with being able to control your body while airborne, then trying to go for grabs.