In the bowl of your standing mixer combine flour, yeast, sugar, and salt, stir to combine. Attach dough hook and on low speed, begin to add pieces of the starter dough, a little at a time. Slowly, begin to add beer. As the dough begins to form, increase the speed to medium and continue to knead until smooth and elastic, about 10 minutes. Transfer to an oiled bowl, cover with plastic wrap and set aside in a warm place allow to rise until doubled in size about one to one and half hours.
Divide dough into six equal parts. Form into smooth ball. Using the palm of your hand, gently flatten each dough ball and then form into a football shape Take each end and stretch the formed dough to 6 inches in length. Place each formed roll onto a parchment lined sheet pan. Score the top of each roll with a sharp knife or blade. Cover and set aside in a warm place to rise for 40 minutes.
Dissolve ½ teaspoon kosher salt in 1 teaspoon water; set aside.
Towards the end of rising time, preheat oven to 400 degrees. Place a sheet pan on the bottom rack of oven and fill it with hot water.
Carefully brush the bolillos with the saltwater solution and place in oven on middle rack. Bake until golden brown, about 20 to 25 minutes, or until an instant-read thermometer inserted into the center registers at least 190 degrees. Cool on a wire rack.