Help with pinch Harmonics on Guitar?

All my electrics I leave at my dad's house, so im stuck with my acoustic/electrics, but i have no amp here. (im at my girlfriends house, her mom lets me stay) anyways, im trying to play pinch harmonics for this song.. I never bothered to learn the technique since i've never ran into them (wierdly) cause i listen to Death Metal//Power Violence. Crap like that (and also a share of bands like Falling In Reverse, RATM, Iron Maiden, and all those genres descending from screamo like Saetia, La Quiete, Raein, Orchid and **** too haha. Anyways.. Im stuck with an acousitc. I dont know if ive mastered it.. I hear a screeching noise.. But its very soft.. Is this because its an acoustic or am i not doing it right to make it sound loud or what? Im confused.. I just pick the string and slightly rub my thumb almost instantly like my gfs dad told me to.. Is this all that you do or is there other ways or what? ARE there any other ways? If so what are they? And are they supposed to sound soft on an acoustic? Id imagine amplified they would sound killer but idk if im doing it right. Oh and if i sound like i have a trashy life.. I dont haha i graduated highschool at 16 and wanna become a surgeoun and **** but I have a huge interest in guitar so yeah. Im trying to learn while I have free time!! and if i posted something confusing sorry I'm on my iPhone. haha