You have to be very careful with the sand or you'll destroy the spindle and fire board much more quickly than when both are in contact with nothing else in between. Essentially you're adding an abrasive to the mix. The larger the grit, the more you'll wear away with each spin much like sandpaper. Also, sand will quickly wear grooves into both the spindle and fire board and that reduces the area of friction.

I usually only use sand if I've managed to burnish the wood and I want to rough it up quickly and break through the polish and compression. After I break through, I clean the sand out.

YMMV of course.

Regarding woods that you can use in Virginia (incomplete):
Cottonwood
Weeping Willow
Sassafras
Basswood
Maple
White Cedar
Red Cedar
Ash
Aspen
Various Poplars
Eastern Hemlock (as sap free as possible)
Staghorn Sumac (not poison sumac LOL)

Hardwoods have high ignition temperatures and the firs, spruces and pines tend to be very resinous, so you might want to stay away from them to start. People with more gumption than I have gotten many of types of all of these to produce coals though so it's not impossible.