Following your advice, got most of the raised parts off with the radius then folded the paper over my fingers to concentrate on the problem areas. Got 9/10 of the depressions smooth, then



Maybe 10 passes too many, and the same in a smaller area a little further down. Making steady progress though, so no complaints - it's a little better each time. It seems that very, very thin is the way to go with each coat. Next thin coat is on and dried, so I'll attack it in a bit and see how it goes.

Not about the fretboard now - if I decided to use Wudtone, how does the application differ from Dingotone?