Select Race Now mode, choose a truck race, set the length to 100%, and choose Bristol as the track. Turn all damage, flags, and wear off. Start the race and drive. You will literally drive through the other trucks on the track. The race is 200 laps and should only take about 45 minutes to complete. When you win, you will be at least 20 laps ahead and get an easy 100 Gamerscore points.