Also, a bit long but very scenic.
Follow the Moderator's Route#2 but do not get off I-81.
Continue on I-81 to I-77 near Wytheville, VA
I-77 South to Columbia, SC
In Columbia pick up I-26 and take it to I-95
Getting close but still not there unless you only want interstates.
Stay on I-77 and don't get off on I-26 but take it 2 miles further to the end. It will drop you off on Hwy 321. Take this to I95 in Hardeeville. This will avoid the I26 section from I77 to I95 which is really starting to become a pain about 1/2 the time. It will also avoid I95 which is already a pain half the time. 321 is a nice backroad and dual lane in the Columbia area.
Since you so much time, you could pick up Shenadoah Skyline at Front Royal just off I-66. At the southern end it turns to the Blue Ridge Parkway. Follow that as far as I77 or if you are having fun, I26 which you can take down to Columbia or I95.