The best way to clean your fretboard is to loosen all the strings & pull them off the fretboard, to either side of the nut. Then use the finest steel wool, grade 0000, to wipe away the oil, grit & dirt that accumulates on the fingerboard and around the frets.
This and other tips on maintaining your guitar is in a new video at the web site.
It’s called ‘Nylon String Guitar Care’ by Ron Fernandez. Ron is a guitar maker and knows how to keep guitars in great condition.
Also new is a DVD I made called ‘How to String & Tune a Guitar.’ To keep the strings from slipping, you need to secure both ends of a nylon-string guitar with the weight of the string on itself. For steel strings, you need to make sure the end that goes in by the peg is bent so the ball is not at the bottom of the peg. Otherwise, the peg can come out. How to string a guitar and how to use a guitar tuner are covered in the DVD. Ron also talks about changing nylon string guitars in his video, but not steel string instruments.
Both are found at – worshipguitarclass.com/Products-accessories.html