G'day Red Dirt Bassist (love the username) welcome to the forum. After you have sanded the fingerboard you need to apply 1 or 2 coats of thin super glue to protect it from the string abuse. Mask the sides of the fingerboard so glue doesn't touch the sides. Let each coat cure overnight and then a light sand with 800/1200 grit wet and dry should level the glue nicely. Also order a set of flatwound strings for a fretless bass. Round wounds will chew your fretboard up