I'm setting up my 4-string Ibanez BTB for C standard tuning, basically going BEAD and tuning it halfstep up. Idea is to use the bottom 4 strings out of a light five string set, going with 120 for the thickest string. Issue is that strings can't exactly fit the nut as is at the moment. So - nut filing. Nut is typical plastic Ibanez type. I would really prefer to do this on my own as opposed to taking it to a tech, and I have a few questions: Using actual file or some fine sandpaper? Filing only the sides or the bottom as well? I figure I should probably check the action at the top couple of frets before going lower. What about the corners? Any other useful tips or things to know in advance? I've searched the forum but most threads are quite old and are usually about more subtle adjustments.