Hi Bruce: I didn't see this show, but I can tell you what I have done to fill small cracks in hardwood flooring in the past. The filler I have used is called pastewood filler, which is a fine powder dissolved in a mineral based solvent, with the consistancy of thick pea soup. You apply it with a brush, working it into the small crevices. let firm up, then before it dries, rub it off the surface with a course rubbing cloth like burlap, although I have seen my peers wait for it to get a bit firmer and scrape off the excess with a broad flexible putty knife. Once it hardens, the surface can be sanded, then stained. The pastes I have used in the past (sorry, haven't used them in a while so I don't remember their trade names) seem to stain along with the wood floor, just fine.
Sorry, don't know if adding fine sawdust powder to the filler compound will help.