Note that the portion of Wilson Creek Trail within Grayson Highlands State Park (from the parking area at the camp store to the point where it joins Seed Orchard Road just before the junction with Scales Trail) is off limits to mountain bikes. This segment is not shown on MTB Project.
After you cross Big Wilson Creek from Seed Orchard Road or Scales Trail, this trail begins at first as a gentle climb up to the Virginia Highlands Horse Trail: Scales to Crest Trail. The trail is filled with loose 4-6 inch rocks, so navigating through/around/over them will keep you entertained. It shares its course with a branch of Wilson Creek for a tenth of a mile, so be prepared to get wet.
The level of difficulty increases as you near the intersection with the Virginia Highlands Horse Trail: Scales to Crest Trail because the overall steepness increases considerably. Kudos if you manage to clean the climb.