Different ukes and different strings and such can help with the volume at higher frets. But you should never let anyone tell you you shouldn't do something, like using a pick. I was just playing with a pick a few minutes ago, because I was playing some super high notes on the fretboard and I wanted more of an attack and a clear sound. You should never limit yourself, I also grow out my nails on my right hand, and if you keep the nails at a certain length you can choose whether you want a more pick-like sound, or a skin sound, on specific notes as well, I can pick a chord and choose to use nail on say just the A string, and it will sound different. It's really convienent. In public I think people must think I'm a coke addict or something, but many ukers grow out their nails for that reason. Some just their thumb nail. Sometimes I play too much and will shred up a nail pretty bad and have to cut it down but it's not too bad usually. My middle fingernail is usually pretty short because it gets all chewed up when I do 'chunks'.
