I have had great success using super glue as a grain filler on open pore wood such as oak, walnut and mahogany. I use a old credit card / gift card type plastic to spread the super glue into the pores. Once the glue is dry I sand it back with 320 paper and finish as usual, I prefer tru-oil. This treatment makes oak and mahogany smooth as glass.
Thanks Frank for the information. If you are using super glue to close the pores of the wood does the tru-oil you use just dry on the surface to be able to give you a smooth finish? I figured if it was an oil it would just evaporate over time.
About 8 to 10 hand rubbed coats of thu-oil will give you a semi gloss look and a silky smooth hard feel when fully cured a week or two after last coat. Thu-oil does not evaporate over time but the finish will dull a bit over time and use. A good hand rub with a soft clothe will restore the luster and of course you can can always add another thin coat anytime in the future.
Thanks sparky. Do you also use super glue or do you just use several coats of Tru-Oil as you described above?
Personally, I use 2-3 coats of wipe-on poly and I don't bother grain filling.
I'm a fan of Howard Feed-N-Wax.
Another vote for Tru-Oil . . . but I've never needed to fill either. For a fretboard, six or seven coats is more than enough
While I don't disagree with any of the methods mentioned I think some of you would change your mind if you tried the super glue trick. It dries so fast and can knock 7 coats of anything down to 1 or none. I showed this method on a peace of mahogany to a old school cabinet maker of 50 years. His response was " I guess an old dog can learn new tricks". Try it, you'll like it....super hard,super fast finish.
I watched a video of a luthier using super glue on a piece of walnut and was amazed how well it looked after just a few coats and also how hard the finish turned out. It looked great.
I've used CA glue on mahogany and walnut guitar bodies and it does make an excellent grain filler; I apply with a razor blade FWIW. CA glue also works extremely well to drop fill a ding.
With CBG's though, I'm never looking for a mirror finish or for them to appear 'perfect' in any way. Nothing like that beautiful professional looking instrument you use for your avatar.