For my guitar nails, those being the first three fingernails on my right hand, large-ish clippers and emery boards, and sometimes a little buffing on carpet or jeans. Clear polish or nail hardener on occasion. Since my thumb nail just doesn't grow long enough without getting in the way when doing other work, I use a Blue Chip thumbpick. All the other nails just get cut short with the clippers. Even so, my guitar nails are still on the short side. Long nails make both my guitar life and my other life awkward.