Place 1/2 cup warm water in medium bowl. Stir in yeast; let stand until dissolved, about 5 minutes. Add buttermilk, both sugars, and vegetable oil; mix well.
Mix flour and salt in processor. With motor running, add yeast mixture and process 2 minutes. Spray large bowl with nonstick spray. Scrape dough into bowl (dough will be very sticky). Spray sheet of plastic wrap with nonstick spray; cover bowl with plastic, sprayed side down. Refrigerate dough until slightly puffed and light, about 1 hour.
Line 2 large rimmed baking sheets with parchment paper, then spray parchment with nonstick spray. Transfer dough to lightly floured surface. Spray hands with nonstick spray. Divide dough into 8 equal portions. Working with 1 portion at a time, roll into 8- to 9-inch ling rope. Tie in knot, leaving 1/2 inch of 1 end sticking up through center. Tuck other end under, if needed (each pretzel will be about 2 3/4 inches in diameter). Transfer pretzels to prepared baking sheets, knob side up. Cover pretzels with plastic wrap sprayed with nonstick spray. Refrigerate until puffed and light, 45 minutes to 1 hour.
Meanwhile, place 1 rack in top third and 1 rack in bottom third of oven; preheat to 450°F Bring 8 cups water, beer, baking soda, and brown sugar to simmer in large wide pot (liquid should reach depth of at least 1 1/2 inches).
Spray 2 baking sheets with nonstick spray. Cut parchment paper between pretzels so each rests on its own square. Using paper to lift pretzels from baking sheet and working with 2 pretzels at a time, carefully invert each pretzel into liquid in pot, allowing to slide off paper. Poach 10 seconds. Using skimmer or slotted spoon, turn pretzels over; poach 10 seconds longer. Lift from poaching liquid, allowing pretzel to drain well. Transfer to prepared sheets. Brush with vegetable oil and sprinkle with pretzel salt.
Bake pretzels 15 minutes, until pretzels are deep brown. (Rotate baking sheets halfway through baking time.) Transfer pretzels to rack; let cool to room temperature.
Can be made 8 hours ahead. Let stand at room temperature.