: How about mixing up a small amount of epoxy, add the sanding dust and mixing
: some fumed silica gradually, stirring well, a little of each, till the
: stiffer then peanut butter goo is about the same color as the wood, then
: smear onto the gaps, then squeegee the excess off?

I would mix up a small amount of epoxy with some sanding dust (no silica) This should be a moderatly stiff peanut butter consistancy, 'cause the dry wood will wick out some of the epoxy; stiffining up the mixture.
force it into the cracks as you would with putty. let it set to the green stage, then scrape (don't sand) it faired. then finish with your satureation coat and continue as normal