HELP!!!!!!

Hey, I need some help, I,ve been playing guitar for two years now and i practice 2 or 3 hours a day and can play most songs i try to learn but a couple months ago i learned how to play a pinch harmonic, i didn't have much succes with it but i can get it usually cleanly on the g string but on the others i dont have much luck. Anyway i need to learn how to get it on all the strings to play some songs, How should i go about practicing and advancing my pinch harmonic skills?