I cleaned another ebony fretboard with "Gorgomyte", the stuff works. I try not to get it on the wood, just the frets and an unbelievable amount of black comes off, more than you would think, like some chemical reaction, afterward I oil the board. Haven't tried it on rosewood yet. My frets are like mirrors and so smooth (like butter). It's worth a try.
No affiliation.
Ralph
No affiliation.
Ralph