Holding the tip of the skewer, take a frozen hot dog and dip it fully into the batter, lifting it out, then rotating it to let excess batter drip off. Using tongs, carefully place the battered dog into the hot oil. Hold it fully submerged for 30-60 seconds until a crust forms, then rotate it so that it fries evenly. Cook for 3-5 minutes, or until golden brown. Repeat with the remaining hot dogs. Serve with mustard for dipping.