A quick look at the map will reveal endless ways to shorten or lengthen the loop, plus it crosses Skyline Drive multiple times, most of which have defined parking areas. Matthews Arm Campground is also nearby if you want to reserve a site and begin there instead.

When hiked clockwise, plan to spend your first night on Piney Branch Trail past the junction with Hull School Trail. You may have to head off this route a little but shouldn't have an issue finding something nearby.

For your second night, find a site on upper Thornton River Trail, but not too close to Skyline Drive. There are few options within one mile of the road, according to the NPS. The Park Service also notes the potential for high water crossings on parts of this route, especially during the spring. Be sure to have this route downloaded on your watch or smart device since there are many trail junctions along the way. A printed map or would also be wise should you need to change plans for any reason.

Sources: https://www.nps.gov/shen/planyourvisit/upload/SHENBCTrip-HogbackMountainandThorntonRiverE044-508.pdf https://en.wikipedia.org/wiki/HogbackMountain(ShenandoahNationalPark,Virginia)