Filing frets (Fret Dressing) is a job for an experienced Luthier or Guitar Technician. If you even get it slightly wrong you will probably want to throw the instrument away.
For fretboard cleaning I prefer a damp cotton Handkerchief, and then a polish with a dry cotton Handkerchief. Commercial cleaning agents such as Lemon oil are available but I was warned off using them on my guitar ( a Martin D18) as they can dry the wood out, which may lead to cracks in the fretboard. Also avoid using wax or aerosol polishes in the guitar body, these polishes can inhibit the quality of the sound, once again, wet hanky, dry hanky.
Cheers!
Arthur
February 2008