I used Zap thin CA to seal my engineered rosewood board. After letting it cure I sanded back, working up to 4000 grade micromesh. I am still a little unhappy with the appearance as I have darker patches close to the frets, but the fretboard now feels as smooth as silk and the loose fibres of the engineered wood are no longer a problem. I can live with the uneven colouration as it is only noticeable in strong light. In normal light it looks a bit like wear from playing. I think that for the best results the board would be sealed without any frets.

But even though I now have a stable and playable board, I would rather have done without the whole process.

DC