Lots of people know about using sawdust and glue, the only issue is that you really need fine dust to make it look its best say from sanding with 220 grit or higher. Your smart to do a test on something first. A couple of other issues is that if this is outdoors you should use Titebond III because its water proof, it still can be an issue outdoors because the sun can discolor your patch particularly the glue. What I always tell my students is the best patch for wood is wood,so I would suggest filling holes with wood plugs . If you don’t have a set of plug cutters you can get a set at a very low cost.
woodworking classes, custom furniture maker