how do I trouble shoot brake lights not working

If it were just the brake lights not working, I'd replace the brake light switch, down on the brake pedal,with a known good one as the fastest, cheapest diag procedure. But, if the brake lights stopped working at the same time that the turn signals stopped working, and the fuses were all okay, I'd first check the switch that controls the emergency flashers. If the flasher switch is partially engaged or is shorted out, then the battery voltage will not go any farther on that circuit than the flasher. Of course, remember that the light bulbs were each probably installed at the same time, so it's not unusual to discover that they each went bad at the same time, too.