Preheat oven to 350ºF with racks in the lower and upper thirds. Combine butter and sugar in a bowl. Using an electric mixer or wooden spoon, beat until light and fluffy. Add lime oil; beat to combine. Gently fold in lime zest, salt, flour, and coconut. Blend well. Lightly flour hands and roll dough into small, approx. 1-in. balls and place about 1-1/2 in. apart on an ungreased baking sheet. Bake until puffy (not browned) and bottoms are just golden, about 15 minutes. Allow cookies to cool on baking sheets for about 5 minutes. Meanwhile, combine coating ingredients in a quart- or gallon-size plastic bag. While cookies are still warm, toss them in the coating. Remove and transfer to wire rack to cool completely. Makes 4 to 5 dozen cookies.