I agree with you about using chemicals. I found a homemade recipes that works well and no chemicals like Round-Up. Dissolve 1 cup salt in a gallon of white vinegar; add 1 Tbsp. soap detergent. Mix well, and spray away. Just keep it off the grass, since it will kill that too. There are other homemade recipes on the internet, but I found this one to be the most effective, but like so many things, YMMV. Sorry I can't help with your original question on the weed dragon ... never used it. I have used 'Grandpa's Weeder' in the past, but I don't think it would work well on the gravel area.
