I have a walnut slab that I'm using for a coffee table. It has a small crack at the edge that at it's maximum is maybe 1.5"-2" wide, but quickly narrows to a 5" long .25" or less wide crack. The slab is 1.5" thick. More for aesthetic purposes than anything else I put a bowtie in the crack.
I've sanded and started finishing the bottom side using emmet's good stuff. The inside of the crack is really hard to get into -- it's super narrow and it takes a few curves in the z-axis (e.g. you can't see through to the other side of the crack in the narrow section. I can see loose wood fibers etc—it's totally unfinished.
Aesthetically it's not a huge deal, but I'd like to seal that wood to prevent moisture from getting in. What's a good way to do that? I can't get a brush or rag through the crack. On top of that the Good Stuff is a super viscous gel that won't drip through. I thought about masking the bottom side, thinning down the Good Stuff till it's runny (alternatively I could use another finish that's less viscous), and letting it just kind of sit in the crack for a bit, but I'm not sure how well that will work.