I am trying to learn power chords because I am learning a bunch of songs that require them. But whenever I try mute the strings with my pointer finger it is really hard and I have to do a bunch of moving with my thumb. Then when I strum it sounds terrible there's a bunch of buzzing and I can hear all the musted strings and not even sure that I can hear the strings I want to hear. I don't know what to do anything would help!