Definitely a challenging great day hike, we did this in May, when the Rhododendrons and Mountain Laurel were starting to bloom. Cedar Ridge is a great uphill and we took a peek inside the Brinegar Cabin. Bluff Mountain trail is a bunch of ups and downs with several good views, hiking in open meadows, plus a nice shelter and some really nice views at Wildcat Rocks Overlook. Sorry to see they have closed Doughton Park visitor center and lodge. Only con about this hike was going down the Flat Rock Ridge trail which was COVERED in spider webs - luckily we had hiking poles we could hold up in front of us to take most of the webs out of the way [sticks will work too]. You can also take the Primitive Trail down which cuts off a couple of miles. As we arrived back at the parking lot on Longbottom Rd, we got hit with a short downpour, but got back in the car quickly. Overall an excellent tour of Doughton Park.
This trail is longer than indicated on Alltrails. It is 4.4 miles one-way from the parking area at Grassy Gap Fire Road to Brinegar cabin, for 8.8 miles round trip. NPS indicates it is over 2000 feet elevation gain while it's probably no more than 2500 feet of elevation change it does seem more than that if you weren't expecting it. The grade is never extremely steep but it is very consistent with few flat spots and multiple switchbacks. Some of the steepest sections were at the very beginning while climbing away from Grassy Gap fire road. There are a few rock outcrops that provide great views overall this was a really enjoyable hike.
I parked by the lodge and hiked from the Wildcat Rocks Overlook to Bluff Mountain and the Alligator Back shelter, before heading back. This part of the trail follows very beautiful mostly open rolling terrain. And the views from the crest of the hills are wonderful, particularly on the spectacular fall day I was lucky to get!