Fretboard Lemon Oil 60ml - Lemon oil for cleaning, conditioning and restoring the keyboard. It easily removes dirt, wax and grease deposits and is delivered in a 60 ml container.
I used it on a Harley Benton that had a fretboard full of dust and dead skin, and after applying the solution, it looks like new. It's quite cheap, worth buying if you want to restore/maintain a guitar.