You can also try the two part epoxy that is sold as super gloss--the pour on finish. I buy mine at Lowes or HD. And it is what I use to fill voids-mixed with whatever mineral I choose. You can mix however much you need and then either use it right then when it's thin to penetrate or wait for a while to let it thicken==up to 20 min or so, depends on ambient temp. If you use it thin, make sure that all the other cracks or holes anywhere close are covered as it can make a heckuva mess (I just know), duct tape works well. And if you don't fill enough, just mix some more to fill in--it adheres to itself well. Only down side is letting it cure for 24 hrs,
I haven't had a failure yet, and I do turn some fairly gnarly pieces.
Hope this helps.