James, I respect your brainstorming ability, on the face it sounds like it could work, but I have handled this stuff before. It's a nightmare.
You'd seal the gaps, but It would be so ugly, so messy, so labor intensive, so expensive, and ugly and messy. Best case, you'd have to go out and cut it back manually, then sand all of both sides of the fence, attempt to refinish it, and a section that tiny sanded smooth, In the end would easily fall out of the cracks within a year.
