I successfully climbed Lightning Peak via Great Western Trail on Nov 3, 2019. Based on my experience, I would revise the route description as follows:
From the GWT parking area, pass the gate at the west end of the parking lot. Walk up the small dirt road for .8 miles, and before you get to the second gate take a left onto a smaller hiking trail. There is no sign at the beginning of the trail. But it is easy to figure it out. The trail splits soon after the beginning. Take the left one. Follow the trail for another 3.5 miles (This distance may be from the trailhead). There is a junction where you need to take the left fork toward Windy Pass. There is no sign at the junction but is a rock in the middle. After another 2 miles you are on top of the pass. There is a sign of the trail number at the pass but no sign of Windy Pass. Turn right (west) and try to stay on the ridgeline (do not go down).