Diy Thundershirt For Dogs . Measure your dog’s length from neck to start of tail. Bring them up behind your dog’s back and tie the two ends snugly, but not too tight.diy anxiety. How To Make A Homemade Thundershirt For Dogs Diy Dog Calming Spray from jaberwockydnalrednow.blogspot.com Fold poster board in half. Measure width of poster board to dog’s length. A diy thundershirt for dogs can be made in a wide variety of ways.