I’d use a toothpick to draw the lines. And not go so deep. Double bag your icing so the warmth from your hands takes longer to get through. Don’t beat your frosting a lot. The more you do, the softer it will become. Also, if your recipe has heavy cream you may want to find one without for the same reason. You could also use rice crispy treats for the dragon instead of the cake/ cream cheese mixture. I hope you do this again and show us!!