Moisten the outer rim of a highball glass with a lime wedge and coat with smoked sea salt (I add chili lime rub from Williams-Sonoma to my rimming salt). Fill half the glass with ice or use an ice ball. Fill a cocktail shaker with ice, then add the tequila, Ancho Reyes, grapefruit juice, and simple syrup. Shake well. Strain into the glass, stir in the soda (I use Topo Chico carbonated mineral water), and garnish with a lime.
Moira brought me to this contrivance.