The North Fork run of the Mayo starts at Moores Mill Road and ends at Anglin Mill Loop Road. It's about a two to two and a half hour paddle through a narrow secluded section containing a few nice ledges, before turning into the Mayo at the confluence with the South Fork, just above the Boiling Hole and S Turn.
The directions I use to get to the Boiling Hole from Mount Airy are ...
Hwy 103 to 8 to 704. In Sandy Ridge, turn left onto Amos Town rd. Follow this 4 mi-5 mi. or so. When you come to a split stay right, which is Anglin Mill rd. You'll cross the mayo and a short distance will be Angiln Mill loop, Dirt rd on right. That will take you down to the boiling hole.