Finally finished the roof. If you attempt this, stay away from my errors
1. Complete roof (including fit) before thatching. Check out the pitch of the roof, how it fits, how it looks before doing any of the thatching.
2. Start with a clean mat. I used a mat we were throwing away, it still had dirt embedded at the bottom which added to the mess.
3. You will make a mess, be sure to do this project on newspaper or something you can periodically sweep up.
4. Be patient. Let one layer dry before laying on the next. Have another project going on or just let it be while it dries.
5. Use something else besides your fingers to press the thatch down into the glue. I cannot tell you how messy it gets when your finger has glue on it and you are picking up every spare piece of mat.
6. Overlay the rows enough to cover the tops of the previous rows but not so much it becomes bulky.
7. Periodically "comb" the thatch to get rid of extra pieces and to check for gaps. I used the open end of a tweezers.
8. If you go with card vs toothpicks, make sure the card stock is thick enough that it won't warp with the glue, wash being added.
That said, I did enjoy doing it and plan to do several more buildings for my Rohan outpost/settlement.