The best I have come up with is 1.5oz epoxy, 2 teaspoons heaping cedar dust, and 2 teaspoons heaping with common white baking flour. Once epoxy glass covered, it blends in pretty well.
I scrape the joints less than 24 hours later with either paint scraper, 3/4 chisel, or 1.25" chisel. Sharpen tools often.
May use less dust and flour for runny mix to get into joints.